Terms and Definitions

Classification Project: Terms and Definitions

Term	Definition(s)
ASDIC	Purportedly an acronym for Allied Submarine Devices Investigation Committee, and a type of SONAR used by the Allies for detecting submarines during the First and Second World Wars. The term has been generically applied to equipment for "under-water supersonic echo-ranging equipment" of submarines and other vessels.
AUVs	, or Autonomous Underwater Vehicles, are underwater robotic vehicles that do not have a tether to the surface. They are preprogrammed to operate over a particular course or to respond to sensor data or perhaps acoustic commands. Applications include surveying, scientific data collection and mine-hunting.
Aback	(of a sail) Filled by the wind on the opposite side to the one normally used to move the vessel forward. On a square-rigged ship, any of the square sails can be braced round to be aback, the purpose of which may be to reduce speed (such as when a ship-of-the-line is keeping station with others), to heave to, or to assist moving the ship's head through the eye of the wind when tacking. A sudden shift in the wind can also cause a square-rigged vessel to be unintentionally "caught aback" with all sails aback. This is a dangerous situation that risks serious damage. In a fore-and-aft-rigged vessel, a headsail is backed either by hauling it across with the weather sheet or by tacking without releasing the sheet. It is used to heave to or to assist with tackingSee also back and fill.
Abaft	Toward the stern, relative to some object (e.g. "abaft the cockpit").
Abaft the beam	Farther aft than the beam; a relative bearing of greater than 90 degrees from the bow; e.g. "two points abaft the beam, starboard side" would describe "an object lying 22.5 degrees toward the rear of the ship, as measured clockwise from a perpendicular line from the right side, center, of the ship, toward the horizon"
Abandon ship	An imperative to leave the vessel immediately, usually in the face of some imminent overwhelming danger. It is an order issued by the master or a delegated person in command, and must be a verbal order. It is usually the last resort after all other mitigating actions have failed or become impossible, when destruction or loss of the ship is imminent, and is customarily followed by a command to "man the lifeboats" or life rafts
Abeam	On the beam; a relative bearing at right angles to the ship's keel; e.g. describing an object located at a bearing of 90 degrees (starboard) or 270 degrees (port) as measured clockwise from the ship's bow
Able seaman (AB)	A merchant seaman qualified to perform all routine duties on a vessel, or a junior rank in some navies. See also able-bodied seaman.
Aboard	On or in a vessel. Synonymous with "on board". See also close aboard.
About	To change the course of a ship by tacking. "Ready about" is the order to prepare for tacking
Above board	On or above the deck; in plain view; not hiding anything. Pirates would often hide their crews below decks, thereby creating the false impression that an encounter with another ship was a casual matter of chance rather than a planned assault.
Above-water hull	The section of a vessel's hull above the waterline; the visible part of a ship. See also topsides.
Absentee pennant	A special pennant flown to indicate the absence of a ship's commanding officer, admiral, chief-of-staff, or an officer whose flag is nonetheless flying (a division, squadron, or flotilla commander).
Absolute bearing	The bearing of an object in relation to north: either true bearing, using the geographical or true north, or magnetic bearing, using magnetic north. See also bearing and relative bearing.
Accommodation ladder	A portable flight of steps down a ship's side.
Accommodation ship	A ship or hull used as housing, generally when there is a lack of quarters available ashore. An operational ship can be used, but more commonly a hull modified for accommodation is used. Also called an accommodation hull.
Act of Pardon	A letter from a state or power authorizing action by a privateer. See also letter of marque. Also Act of Grace.
Action stations	See battle stations.
Administration	The Government of the State whose flag the Ship is entitled to fly or under whose authority the Ship is authorized to operate in the specific case.
Admiralty	2. Another name for admiralty law.
Admiralty law	The body of law that deals with maritime cases. In the UK, it is administered by the Admiralty Court, a special court within the Queen's Bench Division of the High Court of Justice. The Admiralty Court is now in the Rolls Building.
Adrift	1. Afloat and unattached in any way to the shore or seabed, but not underway. When referring to a vessel, it implies that the vessel is not being or able to be controlled and therefore goes where the wind and current take her; a vessel in this condition may also be described as "loose from her moorings" or "out of place". 2. Any gear not fastened down or stored properly.
Advance note	A note for one month's wages issued to a sailor on his signing a ship's articles.
Adviso	See aviso.
Afloat	1. (of a vessel) Floating freely (not aground or sunk). The term may also be used more generally of any floating object or person. 2. In service, even if not currently underway, but not stranded, crewless, in repair, or under construction (e.g. "the company has 10 ships afloat").
Afore	1. In, on, or toward the fore or front of a vessel. 2. In front of a vessel.
Aft	1. Toward the stern or rear of a vessel. Contrast fore. 2. The portion of a vessel behind the middle area of the vessel.
Afterbrow	On larger ships, a secondary gangway rigged in the area aft of midship.
Aftercastle	A stern structure behind the mizzenmast and above the transom on large sailing ships, much larger but less common than a forecastle. The aftercastle houses the captain′s cabin and sometimes other cabins and is topped by the poop deck. See also sterncastle.
Afterdeck	The portion of the deck that is aft of amidships.
Afternoon watch	The afternoon time period between 1200 and 1600 that crew are assigned
Aground	Resting on or touching the ground or land, or the bottom of a body of water (either unintentionally or deliberately, such as in a drying harbor), as opposed to afloat.
Ahead	Forward of the bow.
Ahoo	An adjective indicating an unseamanlike state of disarray. Used to describe something awry, askew, or round but out of true, e.g. "Look at that sad lubberly display! They're still dragging their fenders, and their sails are all ahoo!"
Ahoy	A cry to draw attention. Used to hail a boat or a ship, e.g. "boat ahoy"
Ahull	1. Lying broadside to the sea. 2. To ride out a storm with no sails and helm held to leeward.
Aid to navigation (ATON)	1. Any device external to a vessel or aircraft specifically intended to assist navigators in determining their position or safe course, or to warn them of dangers or obstructions to navigation. 2. Any sort of marker that aids a traveler in navigation, especially with regard to nautical or aviation travel. Such aids commonly include lighthouses, buoys, fog signals, and day beacons.
Air Heater	Shell, uptake and fan outlets comprise the largest components of a system designed to heat the air to prevent condensation and icing.
Aircraft carrier	A warship designed with a primary mission of deploying and recovering aircraft while at sea, thereby acting as a seagoing airbase. Since 1918, the term generally has been limited to a warship with an extensive flight deck designed to operate conventional fixed-wing aircraft. In U.S. Navy slang, also called a "flat top" or a "bird farm". See also carrier.
Aka	Structural section of a vessel that joins the hulls of a multi-hulled vessel together.
Alee	1. On the lee side of a ship. 2. To leeward.
All hands	A ship's entire company, including both officers and enlisted personnel
All night in	Having no night watches.
All standing	Bringing a person or thing up short; i.e. an unforeseen and sudden stop
Allision	The impact of a moving vessel with a stationary object (not submerged), such as a bridge abutment or dolphin, pier or wharf, or another vessel made fast to a pier or wharf. More than incidental contact is required. The vessel is said to "allide" with the fixed object and is considered at fault. Contrast collision.
Aloft	1. In the rigging of a sailing ship 2. Above the ship's uppermost solid structure
Alongside	By the side of a ship or pier
Ama	A secondary hull or float attached to the primary hull of a vessel for stability, or the hulls of a modern catamaran.
Amidships	1. A position half way along the length of a ship or boat. 2. A position half way between the port and starboard sides of a ship or boat, as in "helm amidships", when the rudder is in line with the keel.
Anchor	1. Any object designed to prevent or slow the drift of a ship, attached to the ship by a line or chain; usually a metal, hook, or plough-like object designed to grip the solid seabed under the body of water. See also sea anchor. 2. To deploy an anchor (e.g. "she anchored offshore").
Anchor ball	A round, black shape hoisted in the forepart of a vessel to show that it is anchored.
Anchor buoy	A small buoy secured to a line attached to the crown of an anchor. The line allows the anchor to be unhooked from an obstruction, such as a rock or another vessel's anchor cable, thus preventing raising the anchor in the normal way.
Anchor chain	A chain connecting a ship to an anchor. See also anchor cable.
Anchor detail	A group of men who handle ground tackle when the ship is anchoring or getting under way.
Anchor home	When the anchor is secured aboard the ship for sea; i.e. when it is not deployed. Typically rests just outside the hawsepipe on the outer side of the hull, at the bow of a vessel.
Anchor light	A white light displayed by a ship to indicate that it is at anchor. Two such lights are displayed by a ship over 150 feet (46 m) in length.
Anchor rode	Also referred to as rode. The anchor line, rope, or cable connecting the anchor chain to the vessel.
Anchor sentinel	A separate weight on a separate line that is loosely attached to the anchor rode so that it can slide down it easily. It is made fast at a distance slightly longer than the draft of the boat. It is used to prevent the anchor rode from becoming fouled on the keel or other underwater structures when the boat is resting at anchor and moving randomly during slack tide. See also kellet.
Anchor watch	The crewmen assigned to take care of a ship while it is anchored or moored, and charged with such duties as making sure that the anchor is holding and the vessel is not drifting. Most marine GPS units have an anchor watch alarm capability.
Anchor winch	A horizontal capstan in the bow used for weighing anchors.
Anchor's aweigh	Said of an anchor to indicate that it is just clear of the bottom and that the ship is therefore no longer anchored.
Anchorage	Any place suitable for a ship to anchor, often an area of a port or harbor.
Andrew	Traditional lower-deck slang term for the Royal Navy.
Anemometer	An instrument used to measure wind speed.
Aneroid barometer	An instrument used to measure air pressure, often with the aim of predicting changes in weather
Angle of attack	The angle between the apparent wind and the chord line of the sail.
Angle on the bow	A naval submariner's term for the angle between a target's course and the line of sight to the submarine. It is expressed as port or starboard, so never exceeds 180 degrees. This is one of the figures entered into the Torpedo Data Computer that makes all the calculations necessary for a torpedo attack on the target. Not to be confused with doubling the angle on the bow.
Annex, Code, Convention And Protocol	The above stand out as the most confusing among the myriads of ship terms and definitions. Let us look at what each one stands for. ... (more at Annex, Code, Convention And Protocol)
Answer	The expected response of a vessel to control mechanisms, such as a turn "answering" to the wheel and rudder. "She won't answer" might be the report from a helmsman when turning the wheel under a pilot's order fails to produce the expected change of direction.
Anti-fouling	Anti-fouling is the process of eliminating obstructive organisms from essential components of seawater systems. Depending on the nature and location of marine growth, this process is performed in a number of different ways: ... (more at Anti-fouling)
Anti-rolling tanks	A pair of fluid-filled tanks mounted on opposite sides of a ship below the waterline. The tanks are cross-linked by piping or ducts to allow water to flow between them and at the top by vents or air pipes. The piping is sized so that as the fluid flows from side to side it damps the amount of roll.
Apeak	More or less vertical. Having the anchor rode or chain as nearly vertical as possible without freeing the anchor.
Aport	Toward the port side of a vessel.
Apparent wind	The combination of the true wind and the headwind caused by the boat's forward motion. For example, it causes a light side wind to appear to come from well ahead of the beam.
Apron	A piece of wood fitted to the after side of the stem post and the fore side of the sternpost of a clinker-built boat, where the planking is secured.
Arc of visibility	The portion of the horizon over which a lighted aid to navigation is visible from seaward.
Archboard	A plank along the stern where the name of a ship is commonly painted.
Arctic Engineering	In designing systems that operate in the arctic (especially scientific equipment such as meteorological instrumentation and oceanographic buoys ), marine engineers must overcome an array of design challenges. Equipment must be able to operate at extreme temperatures for prolonged periods of time, often with little to no maintenance. This creates the need for exceptionally temperature-resistant materials and durable precision electronic components. ... (more at Arctic Engineering)
Armament	A ship's complement of weapons.
Armor belt	See belt armor.
Armory	Area on a warship for storage of small arms and ammunition.
Articles of War	Regulations governing the military and naval forces of the UK and US; read to every ship's company on commissioning and at specified intervals during the commission.
As the crow flies	As measured by a straight line between two points (which might cross land), in the way that a crow or other bird would be capable of traveling rather than a ship, which must go around land. Also called great circle.
Ashore	1. On the beach, shore, or land (as opposed to aboard or on board a vessel). 2. Towards the shore.
Assembly station	See muster station.
Astarboard	Toward the starboard side of a vessel.
Astern	1. Toward the stern or rear of a vessel. 2. Behind a vessel.
Astern gear	The gear or gears that, when engaged with an engine or motor, result in backwards movement or force. Equivalent to reverse in a manual-transmission automobile.
Asylum harbor	A harbor used to provide shelter from a storm. See harbor of refuge.
Athwart	From side to side, often in an oblique manner, across or over, as from one side of the vessel to the other, perpendicular to along the length of the hull
Athwartships	At right angles to the fore and aft or centerline of a ship.
Atlantic bow	A raised bow with noticeable sheer and flare introduced in German warships in the late 1930s to improve seakeeping by keeping the forecastle drier and to allow easier operation of weapons.
Auxiliary ship	A naval ship designed to operate in any number of roles supporting combatant ships and other naval operations, including a wide range of activities related to replenishment, transport, repair, harbor services and research. See also auxiliary.
Avast	Stop, cease or desist from whatever is being done. From the Dutch hou' vast ("hold on"), the imperative form of vasthouden ("to hold on to") or the Italian word basta. Compare Ya basta.
Aviso	A kind of dispatch boat or advice boat, surviving particularly in the French Navy. They are considered equivalent to modern sloops. Formerly spelled as adviso.
Awash	So low in the water that the water is constantly washing across the surface.
Aweigh	The position of an anchor that is just clear of making contact with the bottom.
Axial fire	Fire oriented towards the ends of the ship; the opposite of broadside fire. In the Age of Sail, this was known as "raking fire".
Aye, aye
Azimuth circle	An instrument used to take the bearings of celestial objects.
Azimuth compass	An instrument employed for ascertaining the position of the Sun with respect to magnetic north. The azimuth of an object is its bearing from the observer measured as an angle clockwise from true north.
Azimuth thruster	A steerable drive leg fitted through the bottom of a hull, carrying a propeller. Compare stern drive and sail drive.
B & R rig	A style of standing rigging used on sailboats that lacks a backstay. The mast is said to be supported like a "tripod", with swept-back spreaders and a forestay. Used widely on Hunter brand sailboats, among others. Designed and named by Lars Bergstrom and Sven Ridder.
Back	1. To make a sail fill with wind on the opposite side normally used for sailing forward. A fore and aft headsail is backed by either not moving the sail across when tacking, or by hauling it to windward with the weather sheet. A square sail is backed by hauling the yards round with the braces. The sail is then aback. 2. (With oars) to push against the water with the oar in the opposite direction than normally used for moving the boat forward. This is used to slow the speed of the boat, or to move astern when maneuvering.
Back and fill	A method of keeping a square-rigged vessel under control while drifting with the tide along a narrow channel. The ship lies broadside to the current, with the main topsail backed and the fore and mizzen topsail full: essentially a hove-to position. Selective backing and filling of these sails moves the ship ahead or astern, allowing it to be kept in the best part of the channel. A jib and the spanker are used to help balance the sail plan. This method cannot be used if the wind is going in the same direction and at the same speed as the tide.
Back wash	Water forced astern by the action of the propeller. Also, term applies to the receding of waves.
Backstay	A stay or cable, reaching from the mast heads, of the topmast, the topgallant-mast the royal-mast, the skysail-mast to the ship's side abaft the lower rigging; used to support the mast.
Baggywrinkle	A soft covering for standing rigging (such as shrouds and stays) that reduces sail chafing.
Bail out	Tacking away from other boats to obtain clear air. Often used for starting situations.
Bailer	Any device for removing water that has entered a vessel.
Balance rudder	Actually not a single rudder, but a set of three or four rudders operating together to maneuver a sternwheel steamboat. Placed just forward of the paddlewheels, the effectiveness of the balance rudder is increased by the flow of water generated by the paddles, giving such steamboats a high degree of maneuverability.
Baldie
Ballast	Heavy material that is placed in a position low in the hull to provide stability. It can be moveable material, such as gravel or stones, permanently or semi-permanently installed, or integral to the hull, such as the (typically) lead or cast-iron ballast keel of a sailing yacht. See also in ballast.
Ballast tank	A compartment which can be filled or partly filled with water, used on ships, submarines and other submersibles to control buoyancy and stability.
Balls to four watch	U.S. Navy slang for the 0000–0400 watch.
Baltimore Clipper
Bank	A large area of elevated sea floor, deep enough to allow navigation.
Banyan	A traditional Royal Navy term for a day or less of rest and relaxation.
Bar
Bar pilot	A navigator who guides a ship over dangerous sandbars at the mouths of rivers and bays.
Barber hauler	A technique of temporarily rigging a sailboat lazy sheet so as to allow the boat to sail closer to the wind; i.e. using the lazy jib sheet to pull the jib closer to the midline, allowing a point of sail that would otherwise not be achievable.
Barbette	1. A fixed armored enclosure protecting a ship's guns aboard warships without gun turrets, generally taking the form of a ring of armor over which guns mounted on an open-topped rotating turntable could fire, particularly on ships built during the second half of the 19th century. 2. The inside fixed trunk of a warship's turreted gun-mounting, on which the turret revolves, containing the hoists for shells and cordite from the shell-room and magazine, particularly on ships built after the late 19th century.
Barca-longa	A two- or three-masted lugger used for fishing on the coasts of Spain and Portugal and more widely in the Mediterranean Sea in the late 17th and 18th centuries. The British Royal Navy also used them for shore raids and as dispatch boats in the Mediterranean.
Bare poles	Sailing without any canvas raised, usually in a strong wind.
Bareboat charter	An arrangement for the chartering or hiring of a vessel, whereby the vessel's owner provides no crew or provisions as part of the agreement; instead, the people who rent the vessel are responsible for crewing and provisioning her.
Barge	1. A towed or self-propelled flat-bottomed boat, built mainly for river, canal or coastal transport of heavy goods. 2. Admiral's barge: A boat at the disposal of an admiral for his or her use as transportation between a larger vessel and the shore, or within a harbor.
Barge slip	A specialized docking facility designed to receive a barge or car float that is used to carry wheeled vehicles across a body of water.
Bark	An alternate spelling of barque.
Barkentine	An alternate spelling of barquentine.
Barometer	An instrument for measuring air pressure. Used in weather forecasting.
Barque	Also spelled bark. A sailing vessel of three or more masts, with all masts square-rigged except the sternmost, which is fore-and-aft-rigged.
Barquentine	Also spelled barkentine. A sailing vessel with three or more masts, with all masts fore-and-aft-rigged except the foremast, which is square-rigged.
Barrack ship	A ship or craft designed to function as a floating barracks for housing military personnel.
Barratry	In admiralty law, an act of gross misconduct against a shipowner or a ship's demise charterer by a ship′s master or crew that damages the ship or its cargo. Acts of barratry can include desertion, illegal scuttling, theft of the ship or cargo and committing any actions that may not be in the shipowner's or demise charterer′s best interests.
Barrelman	A sailor stationed in the crow's nest.
Batten	1. A stiff strip used to support the roach of a sail, increasing the sail area. 2. Any thin strip of material (wood, plastic, etc.).
Batten down the hatches	To prepare for inclement weather by securing the closed cargo hatch covers with wooden battens so as to prevent water from entering from any angle.
Batteries	: All types of batteries used topside (out of water) can also be used undersea. There are a few factors unique to using batteries underwater. One is that some batteries can produce gases that are potentially explosive. In the open air this is usually not a problem because the small volume of off-gases is quickly diluted. However, in sealed pressure housing, gas build-up can cause problems ranging from water leaks to explosive failure. Pressure relief valves can safely vent gas to eliminate these problems. Some batteries and other subsea electronics use pressure-balanced, oil-filled packaging. In this method, all air spaces and voids in a housing are filled with oil or hydraulic fluid. A flexible membrane on the housing transmits ambient water pressure through the housing. Because the pressure inside the housing is the same as the outside water pressure, it is said to be equalized. Since there is no pressure gradient, a heavy pressure-proof housing is not required. ... (more at Batteries)
Battle stations	Also general quarters or action stations. 1. An announcement made aboard a naval warship to signal the crew to prepare for battle, imminent damage, or any other emergency (such as a fire).
Battlecruiser	A type of large capital ship of the first half of the 20th century, similar in size, appearance, and cost to a battleship and typically armed with the same kind of heavy guns, but much more lightly armored (on the scale of a cruiser) and therefore faster than a battleship but more vulnerable to damage.
Battleship	A type of large, heavily armored warship of the second half of the 19th century and first half of the 20th century, armed with heavy-caliber guns and designed to fight other battleships in a line of battle. It was the successor to the ship-of-the-line used during the Age of Sail.
Beach	Or the beach. A term used broadly to refer to land or the shore, and not necessarily literally to a beach. For example, a ship which turns toward the shore can be said to have turned toward the beach, and a person or object on land can be said to be on the beach. See also on the beach.
Beaching	Deliberately running a vessel aground so as to load or unload it (as with landing craft), or sometimes to prevent a damaged vessel from sinking or to facilitate repairs below the waterline.
Beacon	A lighted or unlighted fixed aid to navigation attached directly to the Earth's surface. Examples include lighthouses and daybeacons.
Beakhead	1. The ram on the prow of a fighting galley of ancient and medieval times. 2. The protruding part of the foremost section of a sailing ship of the 16th to the 18th centuries, usually ornate, which was used as a working platform by sailors handling the sails of the bowsprit. It also housed the crew's heads (toilets).
Beam	The width of a vessel at its widest point, or a point alongside the ship at the midpoint of its length.
Beam ends	The sides of a ship. To describe a ship as "on her beam ends" may mean the vessel is literally on her side and possibly about to capsize; more often, the phrase means the vessel is listing 45 degrees or more.
Beam reach	Sailing with the wind coming across the vessel's beam. This is normally the fastest point of sail for a fore-and-aft-rigged vessel.
Beam sea	A sea in which waves are moving perpendicular to a vessel's course.
Beam wind	A wind blowing perpendicular to a vessel's course.
Bear	A large, squared-off stone used with sand for scraping wooden decks clean.
Bear down	Also bear away, bear off, or fall off.To turn or steer a vessel away from the wind, often with reference to a transit.
Bear up	To turn or steer a vessel into the wind.
Bearing	The horizontal direction of a line of sight between two objects on the surface of the Earth. See also absolute bearing and relative bearing.
Beat to quarters	Prepare for battle (in reference to beating a drum to signal the need for battle preparation).
Beating or beat to	Sailing as close as possible towards the wind (perhaps only about 60°) in a zig-zag course so as to attain an upwind direction into which it is otherwise impossible to sail directly. See also tacking.
Becalm	To cut off the wind from a sailing vessel, either by the proximity of land or by another vessel.
Becalmed	Unable to move due to a lack of wind, said of a sailing vessel; resigned merely to drift with the current rather than to move by controlled management of sails.
Becket	A short piece of line usually spliced into a circle or with an eye on either end.
Before the mast	Literally, the area of a ship before the foremast (the forecastle). Most often used to refer to men whose living quarters are located here: officers were typically quartered in the sternmost areas of the ship (near the quarterdeck), while officer-trainees lived between the two ends of the ship and became known as "midshipmen". Crew members who started out as seamen and then became midshipmen, and later, officers, were said to have gone from "one end of the ship to the other". See also hawsepiper.
Belay	1. To make a fast line around a fitting, usually a cleat or belaying pin. 2. To secure a climbing person in a similar manner.
Belaying pin
Bell	See ship's bell.
Bell buoy	A type of buoy with a large bell and hanging hammers that sound by wave action.
Bell rope	A short length of line made fast to the clapper of the ship's bell.
Below	On or into a lower deck.
Below decks	In or into any of the spaces below the main deck of a vessel.
Bend	1. A knot used to join two ropes or lines. See also hitch. 2. To attach a rope to an object.
Bermuda rig or Bermudan rig	A triangular mainsail, without any upper spar, which is hoisted up the mast by a single halyard attached to the head of the sail. This configuration, introduced to Europe about 1920, allows the use of a tall mast, enabling sails to be set higher where wind speed is greater.
Bermuda sloop
Berth	1. A location in a port or harbor used specifically for mooring vessels while not at sea. 2. A safe margin of distance to be kept by a vessel from another vessel or from an obstruction, hence the phrase "to give a wide berth".
Best bower (anchor)	The larger of two anchors carried in the bow; so named as it was the last, "best" hope for anchoring a vessel.
Between the devil and the deep blue sea	See devil seam.
Between wind and water	The part of a ship's hull that is sometimes submerged and sometimes brought above water by the rolling of the vessel.
Bight	1. A loop in a rope or line – a hitch or knot tied "on the bight" is one tied in the middle of a rope, without access to the ends. 2. An indentation in a coastline.
Bilander	Also billander or be'landre. A small European merchant sailing ship with two masts, the mainmast lateen-rigged with a trapezoidal mainsail, and the foremast carrying the conventional square course and square topsail. Used in the Netherlands for coast and canal traffic and occasionally in the North Sea, but more frequently used in the Mediterranean Sea.
Bilge	1. The part of the hull that the ship rests on if it takes the ground; the outer end of the floors. The "turn of the bilge" is the part of the hull that changes from the (approximately) vertical sides of the hull to the more horizontal bottom of the ship. 2. (Usually in the plural: "bilges") The compartment at the bottom of the hull of a ship or boat where water collects and must be pumped out of the vessel; the space between the bottom hull planking and the ceiling of the hold.
Bilge keel	One of a pair of keels on either side of the hull, usually slanted outwards. In yachts, they allow the use of a drying mooring, the boat standing upright on the keels (and often a skeg) when the tide is out.
Bilged on her anchor	A ship that has run upon her own anchor such that the anchor cable runs under the hull.
Bill	The extremity of the arm of an anchor; the point of or beyond the fluke.
Billethead	1. On smaller vessels, a smaller, non-figural carving, most often a curl of foliage, might be substituted for a figurehead. 2. A round piece of timber at the bow or stern of a whaleboat, around which the harpoon line is run out when the whale darts off.
Bimini top	An open-front canvas top for the cockpit of a boat, usually supported by a metal frame.
Bimmy	A punitive instrument.
Binnacle	The stand on which the ship's compass is mounted, usually near the helm, permitting ready reference by the helmsman.
Binnacle list	A ship's sick list. The list of men unable to report for duty was given to the officer or mate of the watch by the ship's surgeon. The list was kept at the binnacle.
Bird farm	United States Navy slang for an aircraft carrier.
Bite	Verb used in reference to a rudder, as in "the rudder begins to bite". When a vessel has steerageway the rudder will act to steer the vessel, i.e. it has enough water flow past it to steer with. Physically this is noticeable with tiller or unassisted wheel steering by the rudder exhibiting resistance to being turned from the straight ahead – this resistance is the rudder "biting" and is how a helmsman first senses that a vessel has acquired steerageway.
Bitt	1. A post or pair of posts mounted on the ship's bow for fastening ropes or cables. 2. A strong vertical timber or iron fastened through the deck beams that is used for securing ropes or hawsers.
Bitt heads	The tops of two massive timbers that support the windlass on a sailing barge.
Bitter end	The last part or loose end of a rope or cable. The anchor cable is tied to the bitts; when the cable is fully paid out, the bitter end has been reached.
Blinker	A searchlight, used for signaling by code. Usually fitted with a spring controlled shutter.
Block	A pulley with one or more sheaves or grooves over which a line is roved. It can be used to change the direction of the line, or in pairs used to form a tackle.
Block, fiddle	A block with two sheaves in the same plane, one being smaller than the other, giving the block a somewhat violin appearance.
Block, snatch	A single sheave block with one end of the frame hinged and able to be opened, so as to admit a line other than by forcing an end through the opening.
Blockship	A vessel sunk deliberately to block a waterway to prevent the waterway′s use by an enemy.
Blue Peter	A blue and white flag (the flag for the letter P) hoisted at the foretrucks of ships about to sail. Formerly a white ship on a blue ground, but later a white square on a blue ground.
Blue water	1. That part of the ocean lying more than a few hundred nautical miles from shore, and thus beyond the outer boundary of green water. 2. More generally, the open ocean or deep sea.
Blue-water navy	1. A navy capable of sustained operations in the open ocean, beyond a few hundred nautical miles from shore. 2. That portion of a navy capable of sustained operations in the open ocean, beyond a few hundred nautical miles from shore.
Bluejacket	Also blue-jacket.
Bluejacket's Manual	A basic handbook for U.S. Navy personnel.
Board	1. To step onto, climb onto or otherwise enter a vessel. 2. The side of a vessel.
Boat	1. Any small craft or vessel designed to float on and provide transport over or under water. 2. Naval slang for a submarine of any size.
Boat hook	A pole with a blunt tip and a hook on the end, sometimes with a ring on its opposite end to which a line may be attached. Typically used to assist in docking and undocking a boat, with its hook used to pull a boat towards a dock and the blunt end to push it away from a dock, as well as to reach into the water to help people catch buoys or other floating objects or to reach people in the water.
Boat keeper	A boatkeeper was a sailor that knew the harbor thoroughly and was able to act as a pilot. He was in command after the last pilot had left to board a ship and brought the pilot boat back to harbor. He was required to know how to use a sextant as he could be 300 miles from port.
Boathouse
Boatsteerer	A member of the crew of a 19th-century whaling ship responsible for pulling the forward oar of a whaleboat and for harpooning whales.
Boatswain	Also bosun. A non-commissioned officer responsible for the sails, ropes, rigging and boats on a ship who issues "piped" commands to seamen.
Boatswain's call	Also bosun's call, boatswain's pipe, bosun's pipe, boatswain's whistle or bosun's whistle. A high-pitched pipe or a non-diaphragm-type whistle used on naval ships by a boatswain, historically to pass commands to the crew but in modern times limited to ceremonial use.
Boatswain's chair or bosun's chair	1. A short board or swatch of heavy canvas, secured in a bridle of ropes, used to hoist a man aloft or over the ship's side for painting and similar work. Modern boatswain's chairs incorporate safety harnesses to prevent the occupant from falling. 2. A metal chair used for ship-to-ship personnel transfers at sea while underway.
Boatswain's pipe	See boatswain's call.
Boatswain's whistle	See boatswain's call.
Boatwright	A maker of boats, especially of traditional wooden construction.
Bob or bobfly	A pennant or flag bearing the owner's colors and mounted on the topsail trunk.
Bobstay	A stay that holds the bowsprit downwards, counteracting the effect of the forestay and the lift of sails. Usually made of wire or chain to eliminate stretching.
Body plan	In shipbuilding, an end elevation showing the contour of the sides of a ship at certain points of her length.
Boiler	A power generation system component that produces steam.
Boiler room	See fire room.
Boilerman	See fireman.
Bollard	From "bol" or "bole", the round trunk of a tree. A substantial vertical pillar to which lines may be made fast. Generally on the quayside rather than the ship.
Bolt rope	A rope, sewn on to reinforce the edges of a sail.
Bombard	Also spelled bombarde. 1. A small, two-masted vessel common in the Mediterranean in the 18th and 19th centuries, similar in design to an English ketch.
Bombay runner	A large cockroach.
Bone in her teeth	A phrase describing the appearance of a vessel throwing up a prominent bow wave while traveling at high speed. From a vantage point in front of the vessel, the wave rising in either side of the bow evokes the image of a dog carrying a bone in its mouth, and the vessel is said to have a bone in her teeth.
Bonnet	An additional strip of canvas laced to the foot of a sail to increase its area in light winds.
Booby	A type of bird that has little fear and therefore is particularly easy to catch.
Booby hatch	A raised framework or hood like covering over a small hatchway on a ship.
Boom	1. A floating barrier to control navigation into and out of rivers and harbors. 2. A spar attached to the foot of a fore-and-aft sail.
Boom crutch	A frame in which the boom rests when the sail is not hoisted.
Boom defense vessel	An alternative term for a net laying ship.
Boom gallows	A raised crossmember that supports a boom when the sail is lowered (and which obviates the need for a topping lift).
Boom vang or vang	A sail control that lets one apply downward tension on a boom, countering the upward tension provided by the sail. The boom vang adds an element of control to sail shape when the sheet is let out enough that it no longer pulls the boom down. Boom vang tension helps control leech twist, a primary component of sail power.
Boomie or booms'l rig	A ketch-rigged barge with gaff (instead of spritsail) and boom on main and mizzen. Booms'l rig could also refer to cutter-rigged early barges.
Boomkin	See bumpkin or boomkin.
Booms	Masts or yards, lying on board in reserve.
Boot-top	The area on the ship's hull along the waterline, usually painted a contrasting color.
Bore, as in bore up or bore away	To assume a position to engage, or disengage, the enemy ships.
Bosun	See boatswain.
Bosun's call	See boatswain's call.
Bosun's chair	See boatswain's chair.
Bosun's pipe	See boatswain's call.
Bosun's whistle	See boatswain's call.
Bottlescrew	A device for adjusting tension in stays, shrouds and similar lines.
Bottom	1. The underside of a vessel; the portion of a vessel that is always underwater. 2. A ship, most often a cargo ship.
Bottom Samplers	are sediment sampling devices. There are many different types of bottom samplers. A box corer can be dropped into the mud to bring back a block of nearsurface sediment. A piston corer can return a cylinder of sediment up to 100 feet (33 meters) long that may encompass several million years of sedimentary history. For researchers especially interested in the seawater-seafloor interface, a gravity corer can return cores up to 20 feet (6 meters) long with little core-top disturbance. Vibracorers use a motor that produces a high-frequency oscillatory vibration to help propel a long core barrel into unconsolidated sediments.
Bottomry	Pledging a ship as security in a financial transaction.
Bow	1. The front of a vessel. 2. Either side of the front (or bow) of the vessel, i.e. the port bow and starboard bow. Something ahead and to the left of the vessel is "off the port bow", while something ahead and to the right of the vessel is "off the starboard bow". When "bow" is used in this way, the front of the vessel sometimes is called her bows (plural), a collective reference to her port and starboard bows synonymous with bow (singular).
Bow chaser	See chase gun.
Bow sea	Seas approaching a vessel from between 15° and 75° to port or starboard.
Bow thruster	A small propeller or water-jet at the bow, used for maneuvering larger vessels at slow speed. May be mounted externally, or in a tunnel running through the bow from side to side.
Bow visor	A feature of some ships, particularly ferries and roll-on/roll-off ships, that allows a vessel's bow to articulate up and down to provide access to her cargo ramp and storage deck near the waterline.
Bow wave	The wave created on either side of a vessel's bow as she moves through the water.
Bowline	1. A type of knot producing a strong loop of a fixed size, topologically similar to a sheet bend. 2. A rope attached to the side of a sail to pull it towards the bow (for keeping the windward edge of the sail steady)
Bowman	The person, in a team or among oarsmen, positioned nearest the bow.
Bowpicker	A gillnetter that fishes by deploying a gillnet from her bow.
Bows on	Said of a vessel directly approaching an observer, e.g., "The ship approached us bows on."
Bows under	Said of a vessel shipping water over her bow, e.g., "The ship was bows under during the storm."
Bowse	To pull or hoist.
Bowsprit	A spar projecting from the bow that is used as an anchor for the forestay and other rigging. On a barge it may be pivoted so it may be steeved up in harbor.
Boxing the compass	To state all 32 points of the compass, starting at north and proceeding clockwise. Sometimes applied to a wind that is constantly shifting.
Boy seaman	A young sailor, still in training.
Brace	On square rigged ships, a line attached to the yard to turn it, for trimming the sail.
Brace abox	To bring the foreyards flat aback to stop the ship.
Brackets	They are supporting members usually between a vertical and horizontal structural member that not only absorbs forces but also creates a continuous load path between members.
Brail	1. To furl or truss a sail by pulling it in towards the mast. "To brail up" or "to hale up the brails" is to stow the sails. 2. A small line used to haul the edges or corners of sails up or in before furling them. In a ship rig, brails are most often found on the mizzen sail.
Brail net	A type of net incorporating brail lines on a small fishing net on a boat.
Brailer	A device consisting of a net of small-mesh webbing attached to a frame, used aboard fishing vessels for unloading large quantities of fish.
Brake	The handle of the pump, by which it is worked.
Brass monkey or brass monkey weather	Used in the expression "it is cold enough to freeze the balls off a brass monkey". Apocryphally, it is often claimed that a brass monkey was a frame used to hold cannon balls, and low temperature would cause the frame to contract to a greater degree than the iron balls and thus allow them to roll off.
Brass pounder	Early 20th-century slang term for a vessel's radio operator, so-called because he repeatedly struck a brass key on his transmitter to broadcast in Morse code.
Breachway	1. The shore along a channel. 2. The whole area around the place where a channel meets the ocean.
Break bulk cargo	Also breakbulk cargo. Goods that must be loaded aboard a ship individually and not in intermodal containers or in bulk, carried by a general cargo ship.
Breaker	1. A shallow portion of a reef over which waves break. 2. A breaking wave that breaks into foam against the shore, a shoal, a rock or a reef. Sailors use breakers to warn themselves of their vessel's proximity to an underwater hazard to navigation or, at night or during periods of poor visibility, of their vessel's proximity to shore.
Breakwater	1. A structure constructed on a coast as part of a coastal defense system or to protect an anchorage from the effects of weather and longshore drift. 2. A structure built on the forecastle of a ship intended to divert water away from the forward superstructure or gun mounts.
Breastrope	A mooring rope fastened anywhere on a ship's side that goes directly to the quay, so that it is roughly at right angles to both.
Breeches buoy	A ring lifebuoy fitted with canvas breeches, functionally similar to a zip line, used to transfer people from one ship to another or to rescue people from a wrecked or sinking ship by moving them to another ship or to the shore.
Bridge	A structure above the weather deck, extending the full width of the vessel, which houses a command center, itself called by association the bridge.
Bridge wing	A narrow walkway extending outward from both sides of a pilothouse to the full width of a ship or slightly beyond, to allow bridge personnel a full view to aid in the maneuvering of the ship, such as when docking.
Brig	1. A vessel with two square-rigged masts. 2. An American term for an interior area of a ship that is used to detain prisoners (possibly prisoners-of-war, in wartime) or stowaways, and to punish delinquent crew members. Usually resembles a prison cell with bars and a locked, hinged door.
Brig sloop	A type of sloop-of-war introduced in the 1770s that had two square-rigged masts like a brig (in contrast to ship sloops of the time, which had three masts).
Brigantine	Also hermaphrodite brig. A two-masted vessel, square-rigged on the foremast but fore-and-aft-rigged on the mainmast.
Brightwork	Exposed varnished wood on a boat or ship.
Bring to	To cause a ship to be stationary by arranging the sails.
Broach	1. When a sailing or power vessel loses directional control when traveling with a following sea. The vessel turns sideways to the wind and waves and in more serious cases may capsize or pitchpole. Advice on dealing with heavy weather includes various strategies for avoiding this happening 2. An unintentional appearance above the surface of all or part of a submerged submarine, a dangerous event when the submarine is in proximity to enemy forces or near any ship which might collide with her.
Broad	Wide in appearance from the vantage point of a lookout or other person viewing activity in the vicinity of a ship, e.g. another ship off the starboard bow with her side facing the viewer's ship could be described as "broad on the starboard bow" of the viewer's ship.
Broad Fourteens	An area of the southern North Sea which is fairly consistently 14 fathoms (84 feet; 26 meters) deep. On a nautical chart with depths indicated in fathoms, it appears as a broad area with many "14" notations.
Broadhorn	An alternate term for a flatboat.
Broadside	1. One side of a vessel above the waterline. 2. All the guns on one side of a warship or mounted (in rotating turrets or barbettes) so as to be able to fire on the same side of a warship.
Brouwer Route	A route used by ships in the 17th century while sailing east from the Cape of Good Hope to the Netherlands East Indies which took advantage of the strong westerly winds in the southern Indian Ocean known as the "Roaring Forties" to speed the trip but required ships to turn north in the eastern Indian Ocean to reach the East Indies. With no accurate means of determining longitude at the time, ships which missed the northward turn ran the risk of being wrecked on the west coast of Australia.
Brow	See gangplank.
Brown water	1. A collective term for rivers and coastal waters. 2. Maritime waters which lie over the continental shelf.
Brown-water navy	1. A navy capable of operating on rivers and/or in coastal environments. 2. That portion of a navy designed and intended to operate on rivers and/or in coastal environments.
Bucket	Alternative name for a paddle on a paddlewheel.
Buffer	The chief bosun's mate (in the Royal Navy), responsible for discipline.
Bug shoe	A length of hardened material placed on a skeg to protect the skeg from damage by shipworms.
Bugeye	A type of sailboat developed in the Chesapeake Bay by the early 1880s for oyster dredging, superseded as the chief oystering boat in the bay by the skipjack at the end of the 19th century.
Bulbous bow	A protruding bulb at the bow of a ship just below the waterline which modifies the way water flows around the hull, reducing drag and thus increasing speed, range, fuel efficiency and stability.
Bulk cargo	Commodity cargo that is transported unpackaged in large quantities.
Bulk carrier	Also bulk freighter or bulker. A merchant ship specially designed to transport unpackaged bulk cargo in its cargo holds.
Bulkhead	An upright wall within the hull of a ship, particularly a watertight, load-bearing wall.
Bulkheads	Bulkheads are vertical partitions or walls arranged either longitudinally or transversely. The arrangement of bulkheads in longitudinal and transverse directions divides the hull into separate compartments, holds, tanks, or spaces. ... (more at Bulkheads)
Bull ensign	Also boot ensign or George ensign. The senior ensign of a U.S. Navy command (i.e., a ship, squadron or shore activity).
Bullseye	A glass window above the captain's cabin to allow viewing of the sails above deck.
Bulwark  (or bulward)	Also bulward.The extension of a ship's side above the level of the weather deck.
Bulwarks	Bulwarks are high projections from the side shell plating or walls above the main deck level for additional protection. They may be of low scantling but do not contribute much to the vessel strength.
Bumboat	A private boat selling goods.
Bumpkin or boomkin	1. A spar, similar to a bowsprit, but which projects from the stern rather than the bow. May be used to attach the backstay or mizzen sheets 2. An iron bar projecting outboard from a ship's side to which the lower and topsail brace blocks are sometimes hooked.
Bunk	A built-in bed on board ship.
Bunker	A container for storing coal or fuel oil for a ship's engine.
Bunker fuel	Also bunkers. Fuel oil for a ship.
Bunt	1. Middle cloths of a square sail. 2. Centre of a furled square sail.
Bunt-gasket	Canvas apron used to fasten the bunt of a square sail to the yard when furled.
Bunting tosser	A signalman who prepares and flies flag hoists. Also known in the United States Navy as a skivvy waver.
Buntline	One of the lines leading from the foot of a square sail over a block at the head and down to the deck; and used to haul it up to the yard when furling.
Buoy	A floating object, usually anchored at a given position and fulfilling one of a number of uses, recognised by a defined shape and color for each, including aids to navigation, warnings of danger such as submerged wrecks or divers, or for attaching mooring lines, lobster pots, etc.
Buoyed up	Lifted by a buoy, especially a cable that has been lifted to prevent it from trailing on the bottom.
Buoys	There are two main classes of buoys: drifting and moored. As the name implies, drifting buoys are not anchored to the seafloor. They are typically used to study currents and circulation patterns. A drogue (a cylindrical or funnel-shaped device) is sometimes added to have the surface buoy follow a subsurface current. ... (more at Buoys)
Burgee	A small flag, typically triangular, flown from the masthead of a yacht to indicate yacht-club membership.
Burgoo	A dish of ships biscuit crumbs and minced salt pork, usually a meal of last resort for officers when other food stores are exhausted.
Burthen	The Builder's Old Measurement, expressed in "tons bm" or "tons BOM", a volumetric measurement of cubic cargo capacity, not of weight. This is the tonnage of a ship, based on the number of tuns of wine that it could carry in its holds. One 252-gallon tun of wine takes up approximately 100 cubic feet, and weighs 2,240 lbs (1 long ton, or Imperial ton).
Butt	Where the butt of one plank joins with the butt of another.
By and large
By the board	Anything that has gone overboard.
C.O. (or CO)	An abbreviation for commanding officer.
CARGOCONTROL	Cargo Control System, an additional Service Notation
COAT-WBT	Coated Water Ballast Tank, an additional Service Notation
CPO country
CTDs	(conductivity temperature depth) measure how the electrical conductivity and temperature of the water column changes relative to depth. Conductivity and temperature information is valuable, because the speed of sound in seawater can be derived from these variables. This is used to correct devices that use sound underwater. CTD data can also be used to calculate water density. Oceanographers use CTDs to study the physical properties of water, which can help them understand currents, mixing, biological processes and other phenomena. For this reason they are one of the most common instruments used by marine scientists. A CTD may be deployed by itself, attached to a submersible, or as part of a larger metal water sampling array known as a rosette, or carousel. Multiple water sampling bottles are often attached to the rosette to collect water at different depths of the cast.
Cabin	An enclosed room on a deck or flat, especially one used as living quarters.
Cabin boy	An attendant to passengers and crew, often a young man.
Cabin cruiser	A type of powered pleasure craft that provides accommodation for its crew and passengers inside the structure of the craft. A cabin cruiser usually is 7.6 to 13.7 meters (25 to 45 ft) in length, with a powered pleasure craft larger than that considered a motor yacht.
Cable	1. An especially large or thick rope. 2. A cable length.
Cable length	Sometimes simply called a cable. A measure of length or distance equivalent to 1⁄10 nautical mile (608 feet; 185 meters) in the United Kingdom and 100 fathoms (600 feet; 183 meters) in the United States; other countries use different equivalents.
Cables	can be electrical, fiber optic, or a combination of the two. Underwater electrical cables date back to the advent of the telegraph the mid 1840s. Hemp, tar and jute were used around conductors. The advent of plastics and other synthetic materials brought about a variety of new cable designs. The components of a typical underwater electrical cable are: • Conductors —the metallic component of cables through which electrical power or electrical signals are transmitted. ... (more at Cables)
Caboose	A small ship's kitchen or galley on deck.
Cabotage	The transport of goods or passengers between two points within the same country, alongside coastal waters, by a vessel or an aircraft registered in another country.
Cage mast	See lattice mast.
Camels	1. Loaded vessels lashed tightly, one on each side of another vessel, and then emptied to provide additional buoyancy that reduces the draft of the ship in the middle. 2. Floating platforms brought alongside for use by yard workers or crew.
Cameras	are used underwater for all sorts of inspections and documentation. Most types of cameras that can be found topside can be housed and used underwater. They are used by divers, on subsea vehicles and as stand-alone devices. Film cameras are rarely used any more because of the limited amount of images that can be stored before the camera must be brought to the surface so the film can be changed. Thus, for still images, digital cameras are usually preferred. Video camera types include color, black and white, and low light. For low light, imaged-intensified CCD cameras are used, as are tube-type cameras known as SITs (silicone intensified targets). Dome port optics are used in some cameras to correct the distortions caused by looking through a flat window underwater. Features to consider when selecting an underwater camera include, fixed vs. zoom lens, field of view, depth capability, resolution and sensitivity.
Can	A type of navigational buoy, often a vertical drum, but otherwise always square in silhouette, colored red in IALA region A (Europe, Africa, Greenland, and most of Asia and Oceania) or green in IALA region B (the Americas, Japan, Korea, and the Philippines). In channel marking its use is opposite that of a nun buoy.
Canal boat	A specialized watercraft designed for operation on a canal.
Canaller	A ship designed to transit the locks of the Welland Canal.
Canoe stern	A design for the stern of a yacht such that it is pointed like a bow, rather than squared off as a transom.
Canvas	A collective term for all of the sails on a vessel; the total area of all sails aboard her may be expressed as the area of her canvas. Care needs to be taken in understanding what may appear to be an area of canvas for a sail; a stated number may be the length of canvas that is needed off the roll, and it was made several different standard widths.
Cap	A fitting or band used to connect the head of one mast to the lower portion of the mast above.
Cap-stay	A backstay leading from a mast cap to the ship's side.
Cape Horn fever	A feigned illness from which a malingerer is pretending to suffer.
Cape Horn roller	Also graybeard. A type of large ocean wave commonly encountered in the stormy seas of the Southern Ocean south of South America′s Cape Horn, often exceeding 60 feet (18.3 m) in height. The geography of the Southern Ocean, uninterrupted by continents, creates an endless fetch that is favorable for the propagation of such waves.
Capital ship	One of a set of ships considered a navy's most important warships, generally possessing the heaviest firepower and armor and traditionally much larger than other naval vessels, but not formally defined. During the Age of Sail, capital ships were generally understood to be ships of the line; during the second half of the 19th century and the 20th century, they were typically battleships and battlecruisers; and since the mid-20th century, the term may also include aircraft carriers and ballistic missile submarines.
Capsize	(of a vessel) To list so severely that the vessel rolls over, exposing the keel. On large vessels, this often results in the sinking of the ship. Compare turtling.
Capstan	A large winch with a vertical axis used to wind in anchors or to hoist other heavy objects, and sometimes to administer flogging over. A full-sized human-powered capstan is a waist-high cylindrical machine, operated by a number of hands who each insert a horizontal capstan bar in holes in the capstan and walk in a circle.
Captain	2. A naval officer with a rank between commander and commodore.
Captain of the Port	1. In the United Kingdom, a Royal Navy officer, usually a captain, is responsible for the day-to-day operation of a naval dockyard. 2. In the United States, a U.S. Coast Guard officer, usually a captain, is responsible for enforcement of safety, security, and marine environmental protection regulations in a commercial port.
Captain's daughter	Another name for the cat o' nine tails, which in principle is only used on board on the captain's (or a court martial's) personal orders.
Car carrier	A cargo ship specially designed or fitted to carry large numbers of automobiles. Modern pure car carriers have a fully enclosed, box-like superstructure that extends along the entire length and across the entire breadth of the ship, enclosing the automobiles. The similar pure car/truck carrier can also accommodate trucks.
Car float	Also railroad car float or rail barges. An unpowered barge with railroad tracks mounted on its deck, used to move railroad cars across water obstacles.
Caravel	Also caravelle. A small, highly maneuverable sailing ship with a lateen rig, used by the Portuguese in the 15th and 16th centuries to explore along the West African coast and into the Atlantic Ocean.
Cardinal	Referring to the four main points of the compass: north, south, east, and west. See also bearing.
Careening	Also heaving down. Tilting a ship on its side, usually when beached, to clean or repair the hull below the waterline.
Cargo liner	Also passenger-cargo ship or passenger-cargoman. A type of merchant ship that became common just after the middle of the 19th century, configured primarily for the transportation of general cargo but also for the transportation of at least some passengers. Almost completely replaced by more specialized cargo ships during the second half of the 20th century.
Cargo ship	Any ship or vessel that carries cargo, goods, and materials from one port to another, including general cargo ships (designed to carry break bulk cargo), bulk carriers, container ships, multipurpose vessels, and tankers. Tankers, however, although technically cargo ships, are routinely thought of as constituting a completely separate category.
Cargoman	A cargo ship.
Carly Caraval (CC)	Abbreviated as CC (Pronounced “Cee Cee”), this is a type of tender vessel that provides multiple functions, including ambulance, supply transport and passenger service, facilitating free movement of seasteaders between the shore and seasteading communities or even between nearby communities. It is often the first vessel to be encountered when visiting a seastead and regardless of the color scheme, a rose will adorn its deck structure or hull to indicate its purpose. See Tender.
Carpenter	1. In the Age of Sail, a warrant officer was responsible for the hull, masts, spars, and boats of a vessel, and also for sounding the well to see if the vessel was making water. 2. A senior rating responsible for all of the woodwork aboard a vessel.
Carpenter's walk	On a tall ship, a is a narrow unlit passageway or bulkhead often with a low (four-foot) ceiling that is fitted around the hull at its waterline. The carpenter's walk allowed the ship's carpenter to tour the entire waterline area of a ship to inspect it for water leaks. Because of its dark and seldom-visited nature and location far below decks, it was also sometimes used by mutinous sailors as a secluded place to plan a rebellion against the ship's officers.
Carrack	Also nau. A three- or four-masted ocean going sailing ship used by Western Europeans in the Atlantic Ocean from the 15th through the early 17th centuries.
Carrier	An aircraft carrier.
Carry on	Resume work or assigned duties.
Cartel	A ship employed on humanitarian voyages, in particular to carry communications or prisoners between belligerents during wartime. A cartel flies distinctive flags, including a flag of truce, traditionally is unarmed except for a lone signaling gun, and under international law is not subject to seizure or capture during her outbound and return voyages as long as she engages in no warlike acts.
Carvel-built	A method of constructing a wooden hull in which planks are butted edge-to-edge on a robust frame, so giving a smooth hull surface; traditionally the planks are not attached to each other, only to the frame, and have only a caulking sealant between them to make them watertight. Contrast clinker-built.
Casing	A light metal structure, usually incorporating a deck, built over the upper surface of a submarine's pressure hull to create a flat surface on which crew members can walk. A feature of submarines built prior to the mid-20th century, but not of more modern submarines.
Cat	1. To prepare an anchor after raising it by lifting it with a tackle to the cathead, prior to securing (fishing) it alongside for sea. An anchor raised to the cathead is said to be catted. 2. The cat o' nine tails.
Cat's paws	Light, variable winds on calm waters producing scattered areas of small waves.
Catamaran	Any vessel with two hulls. Compare trimaran.
Catboat	A cat-rigged vessel with a single mast mounted close to the bow and only one sail, usually on a gaff.
Catenary	Also catenary curve. The curve of a deployed anchor chain.
Catharpin	A short rope or iron clamp used to brace in the shrouds toward the masts so as to give a freer sweep to the yards.
Cathead	A beam extending out from the hull used to support an anchor when raised in order to secure or "fish" it.
Caulk	To create a watertight seal between structures. In traditional carvel construction, this involved hammering oakum (recycled rope fibers) or caulking cotton into the slightly tapered fine gaps between the hull or deck planks and, in older methods, covering with tar. The expansion of the fibers in water tightens up the hull, making it less prone to racking movement, as well as making the joint watertight.
Cavitation	Cavitation is the process of forming an air bubble in a liquid due to the vaporization of that liquid cause by an area of low pressure. This area of low pressure lowers the boiling point of a liquid allowing it to vaporize into a gas. Cavitation can take place in pumps, which can cause damage to the impeller that moves the fluids through the system. Cavitation is also seen in propulsion. Low pressure pockets form on the surface of the propeller blades as its revolutions per minute increase (IIMS, 2015). [21] Cavitation on the propeller causes a small but violent implosion which could warp the propeller blade. To remedy the issue, more blades allow the same amount of propulsion force but at a lower rate of revolutions. This is crucial for submarines as the propeller needs to keep the vessel relatively quiet to stay hidden. With more propeller blades, the vessel is able to achieve the same amount of propulsion force at lower shaft revolutions. ... (more at Cavitation)
Ceiling	Planking attached to the inside of the frames or floors of a wooden hull, usually to separate the cargo from the hull planking itself. The ceiling has different names in different places; e.g. limber boards, spirketting, quickwork, etc. The lower part of the ceiling is, confusingly to a landsman, what you are standing on at the bottom of the hold of a wooden ship.
Celestial navigation
Center of effort	Also center of pressure. The point of origin of net aerodynamic force upon a sail, roughly located in the geometric center of the sail, though the actual position of the center of effort will vary with sail plan, sail trim, or airfoil profile, boat trim, and point of sail.
Center of lateral resistance	The point of origin of net hydrodynamic resistance on the submerged structure of a boat, especially a sailboat. This is the pivot point the boat turns about when unbalanced external forces are applied, similar to the center of gravity. On a perfectly balanced sailboat, the center of effort will align vertically with the center of lateral resistance. If this is not the case, the boat will be unbalanced and will exhibit either lee helm or weather helm and will be difficult to control.
Centerline	An imaginary line down the center of a vessel lengthwise. Any structure or anything mounted or carried on a vessel that straddles this line and is equidistant from either side of the vessel is said to be "on the centerline".
Centreboard	Also centerplate. A wooden board or metal plate which can be pivoted through a fore-and-aft slot along the centerline in the hull of a sailing vessel, functioning as a retractable keel to help the boat resist leeway by moving its center of lateral resistance. Very common in dinghies, but also found in some larger boats. A daggerboard serves the same purpose but slides vertically rather than pivoting.
Chafing	Wear on a line or sail caused by constant rubbing against another surface.
Chafing gear	Material applied to a line or spar to prevent or reduce chafing. See baggywrinkle and puddening.
Chain locker	A space in the forward part of a ship, typically beneath the bow in front of the foremost collision bulkhead, that contains the anchor chain when the anchor is secured for sea.
Chain plates	Iron bars bolted to a ship's side to which the deadeyes or rigging screws of the lower figging and the back-stays are bolted.
Chain-wale	Also the channel. A broad, thick plank that projects horizontally from each of a ship's sides abreast a mast (distinguished as the fore, main, or mizzen channel accordingly), serving to extend the base for the shrouds, which support the mast.
Chains	Small platforms built into the sides of a ship to spread the shrouds to a more advantageous angle. Also used as a platform for manual depth sounding.
Chalupa	1. A small boat that functions as a shallop, water taxi, or gondola. 2. In Portuguese, a small boat used for cabotage, propelled by either oars or sails. Those equipped with sails have a single mast.
Channel fever	1. The impatient excitement in a ship's crew as the end of a voyage becomes imminent. Characteristics include crew members working harder to get the ship sailing faster, off-watch personnel being on deck to keep track of progress, and everyone being packed and in their shore-going clothes (ready to be paid off) the moment the vessel arrives in port. 2. (obsolete usage) A crew member avoiding duties with a feigned illness, usually after leaving port.
Charlie/Charley Noble	The metal stovepipe chimney from a cook shack on the deck of a ship or from a stove in a galley.
Chartered ship	A term used by the British East India Company from the 17th to the 19th centuries for a merchant ship it chartered to make a single, often one-way, voyage between England (later the United Kingdom) and ports east of the Cape of Good Hope, a trade over which the company held a strict monopoly. A charter ship during its single voyage was employed in much the same way as what the company called an extra ship, though the company usually hired charter ships on special terms and for much shorter periods. Also charter ship.
Charthouse	A compartment from which the ship was navigated, especially in the Royal Navy.
Chartplotter
Chasse-marée	A decked commercial sailing vessel engaged in the transportation of fresh fish directly from fishing grounds to ports in Brittany between the 18th century and around the third quarter of the 19th century. Three-masted luggers replaced the vessels originally serving in this role; the luggers then were replaced successively by dundees, brigs, and schooners.
Cheeks	1. Wooden blocks at the side of a spar. 2. Flat plates of iron or wood bolted to the masthead to form angle supports for the cross-trees.
Chemical Sensors	are commonly used to detect hydrocarbons, nutrients (nitrate, nitrite, ammonia, urea, phosphate, silicate, and iron) as well as pH and dissolved oxygen in and on water. A variety of sensing techniques are employed including optical methods.
Chief engineer	The senior engineering officer (abbreviated ChEng).
Chine	1. An angle in the hull. 2. A line formed where the sides of a boat meet the bottom. Soft chine is when the two sides join at a shallow angle, and hard chine is when they join at a steep angle.
Chock	A hole or ring attached to the hull to guide a line via that point; an opening in a ship's bulwark, normally oval in shape, designed to allow mooring lines to be fastened to cleats or bits mounted to the ship's deck. See also Panama chock and Dutchman's chock.
Chock-a-block	Rigging blocks that are so tight against one another that they cannot be further tightened.
Chop	Waves, usually created by the wind, which are smaller and shorter-lived than swell.
Chronometer	A timekeeping device accurate enough to be used aboard a ship to determine longitude by means of celestial navigation. The invention of the marine chronometer in the 18th century was a major technical achievement for maritime navigation.
Cigarette boat	See go-fast boat.
Citadel	A fortified safe room on a vessel to take shelter in the event of pirate attack. Previously, a fortified room to protect ammunition and machinery from damage.
Class	1. Strictly, a group of government ships, especially naval ships, of the same or similar design. 2. Informally, a group of private or commercial ships of the same or similar design.
Classification society	Also classification organization or classification organization. See ship classification society.
Clean bill of health	A certificate issued by a port indicating that a ship carries no infectious diseases. Also called a pratique.
Clean slate	At the helm, the watchkeeper would record details of speed, distances, headings, etc. on a slate. At the beginning of a new watch the slate would be wiped clean.
Clear	1. To perform customs and immigration legal issues prior to leaving port. 2. More loosely, to leave port.
Cleat	A stationary device used to secure a rope aboard a vessel.
Clench	A method of fixing together two pieces of wood, usually overlapping planks, by driving a nail through both planks as well as a washer-like rove. The nail is then burred or riveted over to complete the fastening.
Clew	One of the lower corners of a square sail, or, on a triangular sail, the corner at the end of the boom.
Clewlines	Lines used to truss up the clews, the lower corners of square sails. Used to reduce and stow a barge's topsail.
Clinker-built	A method of constructing hulls that involves overlapping planks and/or plates, much like Viking longships, resulting in speed and flexibility in small boat hulls. Contrast carvel-built.
Clipper	2. A tuna clipper.
Close aboard	Very near (the ship).
Close-hauled	(of a vessel) Beating as close to the wind direction as possible.
Clove hitch	A bend used to attach a rope to a post or bollard. Also used to finish tying off the foresail.
Club hauling	A maneuver by which a ship drops one of its anchors at high speed in order to turn abruptly. This was sometimes used as a means of obtaining a good firing angle on a pursuing vessel. See kedge.
Coal hulk	A hulk used to store coal.
Coal trimmer	A person responsible for ensuring that a coal-fired vessel remains in "trim" (evenly balanced) as coal is consumed on a voyage. Also trimmer.
Coaling	Loading coal for use as fuel aboard a steamship. A time-consuming, laborious, and dirty process often undertaken by the entire crew, coaling was a necessity from the early days of steam in the 19th century until the early 20th century, when oil supplanted coal as the fuel of choice for steamships.
Coaming	The raised edge of a hatch, cockpit, or skylight, designed to help keep out water that pools on the surface above.
Coastal Design and Restoration	Coastal engineering applies a mixture of civil engineering and other disciplines to create coastal solutions for areas along or near the ocean. In protecting coastlines from wave forces, erosion , and sea level rise , marine engineers must consider whether they will use a “gray" infrastructure solution - such as a breakwater, culvert, or sea wall made from rocks and concrete - or a “green” infrastructure solution that incorporates aquatic plants, mangroves, and/or marsh ecosystems. [22] It has been found that gray infrastructure costs more to build and maintain, but it may provide better protection against ocean forces in high-energy wave environments. [23] A green solution is generally less expensive and more well-integrated with local vegetation, but may be susceptible to erosion or damage if executed improperly. [24] In many cases engineers will select a hybrid approach that combines elements of both gray and green solutions. [25] ... (more at Coastal Design and Restoration)
Coaster	A coastal trading vessel; a shallow-hulled ship used for trade between locations on the same island or continent. Also skoot.
Coble	A type of open traditional fishing boat with a flat bottom and high bow which developed on the northeast coast of England.
Cockbill	To angle a square-rigged yard away from the horizontal so that it is out of the way for loading or unloading, or so that the ship may lie alongside another ship without the yards touching.
Cockpit	A seating area (not to be confused with the deck) towards the stern of a small-decked vessel that houses the rudder controls.
Cofferdam
Cog	A type of sailing ship, with a single mast and a single square-rigged sail first developed in the 10th century and widely used, particularly in the Baltic Sea region, in seagoing trade from the 12th through the 14th centuries. It had a distinctive hull design: the flat bottom was carvel-built and the sides were clinker-built.
Coign	A wedge used to assist in the aiming of a cannon; an older form of "quoin".
Collier	A bulk cargo ship designed to carry coal, especially such a ship in naval use to supply coal to coal-fired warships.
Combat loading
Comber	A long, curving wave breaking on the shore.
Come about	1. To tack. 2. To change tack.
Come to	To stop a sailing vessel, especially by turning into the wind.
Commanding officer	The officer in command of a warship. Also called "CO", "captain" (regardless of rank), "skipper", or "the old man".
Commission	To formally place (a naval vessel) into active service, after which the vessel is said to be in commission. Sometimes used less formally to mean placing a commercial ship into service.
Commissioning pennant	A pennant flown from the masthead of a warship. Also called a masthead pennant.
Commodore	1. (rank) Prior to 1997, the title was used in the Royal Navy for an officer of the rank of captain who was given temporary command of a squadron. At the end of the deployment of the squadron, or in the presence of an admiral, he would revert to his de facto rank of captain. 2. (rank) A military rank used in many navies that is superior to a navy captain but below a rear admiral. Often equivalent to the rank of "flotilla admiral" or sometimes "counter admiral" in non-English-speaking navies.
Communication tube	An air-filled tube, usually armored, allowing speech between the conning tower and the below-decks control spaces on a warship. Also speaking tube or voice tube.
Companionway	A raised and windowed hatchway in a ship's deck, with a ladder leading below and the hooded entrance-hatch to the main cabins.
Compasses	Magnetic compasses consist of a small, lightweight magnet balanced on a nearly frictionless pivot point. Magnetic compasses have several problems when used on moving platforms like ships. They must be level, they correct rather slowly when the platform turns, they are influenced by ferrous metals and they indicates magnetic north rather than true north . For these reasons, most ships and airplanes use gyroscopic compasses. A spinning mass gyrocompass has a spinning body with three axes of angular freedom constituting a gyroscope. They can take up to several hours to spin up and stabilize. ... (more at Compasses)
Complement	1. The number of persons in a ship′s crew, including officers. 2. A collective term for all of the persons in a ship′s crew, including officers.
Comprise
Concrete ship	A vessel constructed of steel and ferrocement (a type of reinforced concrete) rather than of more traditional materials, such as steel, iron, or wood.
Condensers
Conn	To direct a ship or submarine from a position of command. While performing this duty, an officer is said to have the conn. Also con, conne, conde, cunde, or cun.
Connectors	are used to join a cable to a device such as an underwater vehicle, instrument or battery; or to join two cables together. They can be used for electrical conductors or optical fibers, or both. There are many types of underwater connectors, some can be mated when wet, others must be dry. Some of the common types are: • Cable Glands —actually not a connector at all but a rubber grommet in a housing that seals around a cable. They are inexpensive and easy to install but are not reliable for long-term immersions or in dynamic situations where the cable will be subject to flexing. ... (more at Connectors)
Conning officer	An officer on a naval vessel responsible for instructing the helmsman on the course to steer. While performing this duty, the officer is said to have the conn.
Conning tower	1. An armored control tower of an iron or steel warship built between the mid-19th and mid-20th centuries from which the ship was navigated in battle. 2. A tower-like structure on the dorsal (topside) surface of a submarine, serving in submarines built before the mid-20th century as a connecting structure between the bridge and pressure hull and housing instruments and controls from which the periscopes were used to direct the submarine and launch torpedo attacks. Since the mid-20th century, it has been replaced by the sail (United States usage) or fin (European and British Commonwealth usage), a structure similar in appearance that no longer plays a role in directing the submarine.
Consort	Unpowered Great Lakes vessels, usually a fully loaded schooner, barge, or steamer barge, towed by a larger steamer that would often tow more than one barge. The consort system was used in the Great Lakes from the 1860s to around 1920.
Constant bearing, decreasing range (CBDR)	When two boats are approaching each other from any angle and this angle remains the same over time (constant bearing) they are on a collision course. Because of the implication of collision, "constant bearing, decreasing range" has come to mean a problem or an obstacle which is incoming.
Container ship	A cargo ship that carries all of her cargo in truck-size intermodal containers.
Convoy	A group of ships traveling together for mutual support and protection.
Corinthian	An amateur yachter.
Corrector	A device used to correct the ship's compass, e.g. by counteracting errors due to the magnetic effects of a steel hull.
Corrosion	results when two dissimilar metals are in contact with each other and are immersed in a conductive solution (i.e., seawater). Corrosion can cause structural failure of materials or cause sealing surfaces to leak; thus, it is a very important engineering concern. The rate of corrosion is determined by several factors, including: • Valence of the metals ... (more at Corrosion)
Corsair	1. A French privateer, especially one from the port of St-Malo. 2. Any privateer or pirate.
Corvette	1. A flush-decked sailing warship of the 17th, 18th, and 19th centuries having a single tier of guns, ranked next below a frigate. In the U.S. Navy, it is referred to as a sloop-of-war. 2. A lightly armed and armored warship of the 20th and 21st centuries, smaller than a frigate and capable of transoceanic duty. Also corvetto.
Cotchel	A partial load.
Cottonclad	A steam-powered wooden warship protected from enemy fire by bales of cotton lining its sides, most commonly associated with some of the warships employed by the Confederate States of America during the American Civil War (1861–1865).
Counter	The part of the stern above the waterline that extends beyond the rudder stock culminating in a small transom. A long counter increases the waterline length when the boat is heeled, increasing hull speed. See also truncated counter.
Counterflood	To deliberately flood compartments on the opposite side from already flooded ones. Usually done to reduce a list.
Country ship
Course	1. The direction in which a vessel is being steered, usually given in degrees. 2. The lowest square sail on a square rigged mast, except where that mast is the mizzen – in which case the name cro'jack (cross-jack) or mizzen-sail is used.
Cowl	1. A ship's ventilator with a bell-shaped top that can be swiveled to catch the wind and force it below. 2. A vertical projection of a ship's funnel that directs the smoke away from the bridge.
Coxswain	The helmsman or crew member in command of a boat. Also cockswain.
Crab	A winch used for raising the leeboard, with a barrel for pulling in the staysail sheets.
Crabber	A fishing vessel rigged for crab fishing.
Cranse iron	The metal fitting is mounted at the end of a bowsprit to which the forestay (or jibstay), bobstay, and bowsprit shrouds are attached. It is also where the tack of the outermost headsail is fastened. Also crance, crans, or cranze iron.
Crash rescue boat or crash boat	A term used in the United States to describe military high-speed offshore rescue boats, similar in size and performance to motor torpedo boats, used to rescue pilots and aircrews of crashed aircraft.
Crazy Ivan	U.S. Navy slang for a maneuver in which a submerged Soviet or Russian submarine suddenly turns 180 degrees or through 360 degrees to detect submarines following it.
Crew	1. On warships and merchant ships, all of those members of a ship's company who are not officers. 2. On leisure vessels with no formal chain of command, all of those persons who are not the skipper or passengers.
Crew boat	A vessel specialized for the transportation of offshore support personnel and cargo to and from offshore installations such as oil platforms, drilling rigs, drill ships, dive ships, and wind farms. Also known as a fast support vessel or fast supply vessel.
Crew management	The services rendered by specialized shipping companies to manage the human resources and manning of all types of vessels, including recruitment, deployment to vessel, scheduling, and training, as well as the ongoing management and administrative duties of seafarers, such as payroll, travel arrangements, insurance and health schemes, overall career development, and day-to-day welfare. Also known as crewing.
Cringle	A loop of rope, usually at the corners of a sail, for fixing the sail to a spar. They are often reinforced with a metal eye.
Cro'jack	The square sail set on the lower mizzen yard of a square-rigged ship. Many full-rigged ships would not set a sail in this position, as it would be interfered with by the spanker.
Cross the line	Cross the equator.
Crosstrees	Two horizontal struts at the upper ends of the topmasts of sailboats, used to anchor the shrouds from the topgallant mast. Lateral spreaders for the topmast shrouds (standing back stays).
Crow's nest	A masthead constructed with sides and sometimes a roof to shelter the lookouts from the weather, generally by whaling vessels. The term has also become generic for what is properly called a masthead.
Cruise ship	A passenger ship used for pleasure voyages, where the voyage itself and the ship's amenities are part of the experience, as well as the different destinations along the way. Transportation is not the prime purpose, as cruise ships operate mostly on routes that return passengers to their originating port. A cruise ship contrasts with a passenger liner, which is a passenger ship that provides a scheduled service between published ports primarily as a mode of transportation. Large, prestigious passenger ships used for either purpose are sometimes called ocean liners.
Cruiser	2. From the early to the mid-20th century, a type of armored warship with varying armament and of various sizes, but always smaller than a battleship and larger than a destroyer, capable of both direct support of a battle fleet and of independent operations, armed with guns and sometimes torpedoes.
Crutches	Metal Y-shaped pins used to fix oars while rowing.
Cuddy	A small cabin in a boat; a cabin, for the use of the captain, in the after part of a sailing ship under the poop deck.
Cunningham
Cunt splice or cut splice	A join between two lines, similar to an eye-splice, where each rope end is joined to the other a short distance along, making an opening that closes under tension.
Cuntline	The "valley" between the strands of a rope or cable. Before serving a section of laid rope, e.g. to protect it from chafing, it may be "wormed" by laying yarns in the cuntlines, giving that section an even cylindrical shape.
Current Meters	are devices that measure water velocity and direction. Measuring currents is a fundamental practice of physical oceanographers. By determining how ocean waters move, scientists can determine how organisms, nutrients and other biological and chemical constituents are transported throughout the ocean. There are several common types of current meters: • Mechanical current meters are like underwater pin wheels. The rate at which the wheel spins is used to calculate the current flow. A drawback to mechanical meters is that they do not work well in weak currents. ... (more at Current Meters)
Cut and run	When wanting to make a quick escape, a ship might cut lashings to sails or cables for anchors, causing damage to the rigging, or losing an anchor, but shortening the time needed to make ready by bypassing the proper procedures.
Cut of his jib	The "cut" of a sail refers to its shape. Since this would often vary between ships, it could be used both to identify a familiar vessel at a distance, and to judge the possible sailing qualities of an unknown one. During the 16th and 17th centuries, the ships of different nations used visually distinctive types of jibs that could be determined at a distance, providing an easy way to determine friend from foe. Also used figuratively of people.
Cutter	1. A sailing vessel defined by its rig. In European waters this is a single-masted fore and aft rig with two or more headsails In North American waters, the definition also considers whether or not the bowsprit is permanently fixed and also takes into account the position of the mast. A standing (permanently fixed) bowsprit and a forward mast position, but with two or more headsails would be classed as a sloop in the North American definition. A running bowsprit, a forestay (carrying a staysail) that is fixed to the stemhead, a jib that is set flying and a mast position that is more aft is a cutter. 2. A type of ship's boat powered by sail or oars, though more optimized for sail than many types of ship's boat.
Cutting out
Cutwater	The forward curve of the stem of a ship.
DIVINGSUPPORT	Diving Support system, an additional Service Notation
DYNOPOS	Dynamic Position System
Daggerboard	A type of light centerboard that is lifted vertically; sometimes in pairs, with the leeward one lowered when beating.
Dan or dan-buoy	A temporary marker buoy consisting of a long pole with flag and/or light at the top and, lower down, a float and a ballast weight to make it float vertically. May be used with or without an anchor to attach it to the sea bed. In naval use often marks a swept channel created by minesweeping. In other uses may mark fishing equipment (nets or pots), an anchor, or, most commonly, is attached to a lifebuoy to throw into the sea to mark the position of a man overboard.
Dandy	1. A rig with a small mizzen abaft the steering post. 2. In British usage, another name for a yawl.
Danlayer
Dart	To run dart; to run dead before the wind.
Data Loggers	are used to acquire and store information from sensors. The entire spectrum of data storage devices used topside have and can be housed in pressure vessels. These include hard disk drives, flash memory, video tape, etc. When brought to the surface, the logged data can be transferred to a computer or the memory can be removed for archiving. Factors to consider when selecting a data logger include how many sensors will be measured, for how long at what sampling rate, how much power is available, how much space is available, etc. Environmental sensors and transducers often measure things such as temperature, pressure, sound or light, as voltages or current levels. These analog signals must be converted to digital ones for use by computers. The conversion, known as A/D conversion, is done by electronic sampling of the analog signals. ... (more at Data Loggers)
Data Multiplexing	is the practice of sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end. In analog transmission, signals are commonly multiplexed using frequency-division multiplexing (FDM) in which the carrier bandwidth is divided into sub channels of different frequency widths, each carrying a signal at the same time in parallel. ... (more at Data Multiplexing)
Data Telemetry	is the process of measuring data at the source and transmitting it automatically. There are many ways to telemeter data back to shore such as by cell phone, radio transmitter, microwave and satellite. There are several satellite services available (ARGOS, Inmarsat, Iridium, GOES, Orbcomm) that can receive data from most anywhere on the planet. Data can be transmitted from a variety of platforms, including moored buoys , drifting floats, and even marine animals. Acoustic modems are used to telemeter data through the water column from a source to a receiver. They rely on coded pulses of sound. Acoustic modems are often used with seafloor sensors to telemeter data to a surface buoy or surface ship. From there the data can be relayed to shore using one of the previously mentioned methods of telemetry.
Davit	1. A spar formerly used on board ships as a crane to hoist the flukes of the anchor to the top of the bow without injuring the sides of the ship. 2. A crane, often working in pairs and usually made of steel, used to lower things over the side of a ship, including lifeboats.
Davy Jones' Locker	An idiom for the bottom of the sea.
Day beacon	An unlighted fixed structure equipped with a dayboard for daytime identification.
Day boat	1. A sailing boat without overnight accommodation, sometimes with a small cabin, used for pleasure sailing. Typically around 20 feet (6.1 m) in length. 2. (United States): a steamboat built for daytime service; as opposed to a night boat.
Day-blink	The moment at dawn where, from some point on the mast, a lookout can see above low-lying mist around the ship.
Dayboard	The daytime identifier of an aid to navigation presenting one of several standard shapes (square, triangle, or rectangle) and colors (red, green, white, orange, yellow, or black).
Dead ahead	Exactly ahead; directly ahead; directly in front.
Dead horse	Debt owed for advanced pay. The "flogging a dead horse" ceremony at sea celebrated discharge of the debt.
Dead in the water	Not moving (used only when a vessel is afloat and neither tied up nor anchored). The term is abbreviated to DIW by the U.S. Navy. It is often used to indicate that a pirate or drug runner vessel has been immobilized.
Dead reckoning
Dead run	See running.
Dead slow	See steerageway.
Dead wake	The trail of a fading disturbance in the water. See also wake.
Deadeye	A wooden block with three holes (but no pulleys) spliced to a shroud. It adjusts the tension in the standing rigging of large sailing vessels, by lacing through the holes with a lanyard to the deck. It performs the same job as a turnbuckle.
Deadhead	A snag.
Deadlight	A strong shutter fitted over a porthole or other opening that can be closed in bad weather.
Deadrise	The angle of the hull surface, relative to horizontal, as measured on either side of the keel on a line drawn towards the turn of the bilge. Without any other qualifier, it is taken at the midships cross-section of the hull. This can be expressed in degrees or sometimes as a vertical linear measure (such as inches) at a standard distance from the keel. A hull with a lot of deadrise has an obvious "V" shape to the bottom of the hull, whereas no deadrise denotes sheer sides and a flat-bottomed hull. It is usually taken to be one of several measures of the "sharpness" of a hull. It can also be referred to as the "rise of the floor".
Deadwood	In a traditional wooden hull, blocks of timber on the top of the keel that forms the shape of the hull where its section is too narrow for the method of construction employed elsewhere. It is often used forward of the sternpost.
Death roll	In a keelboat, the act of broaching to windward, putting the spinnaker pole into the water and causing a crash-gybe of the boom and mainsail, which sweep across the deck and plunge down into the water. During a death roll, the boat rolls from side to side, becoming gradually more unstable until either it capsizes or the skipper reacts correctly to prevent it.
Debarcation or disembarkation	The process of leaving a ship or aircraft, or removing goods from a ship or aircraft.
Debunk	The process of removing fuel from a vessel. After a shipwreck, a "debunkering" operation will be performed in an effort to minimize damage and protect the environment from fuel spills.
Deck	1. The top of a ship or vessel; the surface that is removed to accommodate the seating area. 2. Any of the structures forming the approximately horizontal surfaces in the ship's general structure. Unlike flats, they are a structural part of the ship.
Deck Beams	They are transverse stiffening members running laterally and strengthening the deck plating.
Deck hand	A person whose job involves aiding the deck supervisor in (un)mooring, anchoring, maintenance, and general evolutions on deck. Also called a decky.
Deck supervisor	The person in charge of all evolutions and maintenance on deck; sometimes split into two groups: forward deck supervisor and aft deck supervisor.
Deckhead	The underside of the deck above. The inside of the boat is normally paneled over to hide the structure, pipes, electrical wires. It can be in thin wood planks, often covered with a vinyl lining, or in thin PVC or now even in fiberglass planks.
Deckhouse	A cabin that protrudes above a ship's deck.
Decks awash	A situation in which the deck of the vessel is partially or wholly submerged, possibly as a result of excessive listing or a loss of buoyancy.
Decommission	To formally take (a naval vessel) out of active service, after which the vessel is said to be out of commission or decommissioned. Sometimes used less formally to mean taking a commercial ship out of service.
Deep Sea Systems	Life Support ... (more at Deep Sea Systems)
Degaussing	A process to reduce a warship's magnetic signature.
Density and Specific Gravity	These ship terms are more to do with Tanker Officers and Crew. ... (more at Density and Specific Gravity)
Depot ship	A ship that acts as a mobile or fixed base for other ships and submarines or that supports a naval base.
Depth of hold	The distance between the underside of the main deck (or its supporting beams) and the top of the limber boards (the part of the ceiling that lies alongside the keelson), measured at the middle frame. It is one of the key measurements in working out the measurement tonnage in most systems.
Derrick	A lifting device composed of one mast or pole and a boom or jib hinged freely at the bottom.
Derricks And Cranes	Derricks and Cranes are both ship terms related to lifting appliances. Derricks are now relics of the past and found only on a few older ships. They have been replaced by the more versatile and much simpler Deck Crane. ... (more at Derricks And Cranes)
Despatch	A fee paid by a shipowner to a charter party if the time taken to load or unload a vessel is less than the laytime – the amount of time stipulated for loading or unloading – specified in a voyage charter.
Despatch boat	An alternate spelling of dispatch boat.
Devil seam	The devil was possibly a slang term for the garboard seam, hence "between the devil and the deep blue sea" being an allusion to keel hauling, but a more popular version seems to be the seam between the waterway and the stanchions, which would be difficult to get at, requiring a cranked caulking iron, and a restricted swing of the caulking mallet.
Devil to pay	"Paying" the devil is sealing the devil seam. It is a difficult and unpleasant job (with no resources) because of the shape of the seam (up against the stanchions) or if the devil refers to the garboard seam, it must be done with the ship slipped or careened. Also devil to pay, and no pitch hot.
Devil's claw	A type of chain stopper often used to secure an anchor in its hawsepipe. Consists of a two-pronged hook that fits over a link of chain, a turnbuckle and a short chain fastened to a strong point.
Dhow	The generic name of a number of traditional sailing vessels with one or more masts with lateen sails used in the Red Sea and Indian Ocean region, typically weighing 300 to 500 tons, with a long, thin hull. They are trading vessels primarily used to carry heavy items, like fruit, fresh water, or merchandise. Crews vary from about thirty to around twelve, depending on the size of the vessel.
Diamonds	Glass prisms that were laid between the wooden deck planks to allow natural light below were referred to as diamonds due to the sparkle they gave off in the sunlight.
Dinghy	1. A type of small boat, often carried or towed as a ship's boat by a larger vessel. 2. A small racing yacht or recreational open sailing boat, often used for beginner training rather than sailing full-sized yachts.
Dipping the eye	Dipping the flag. A method of rendering honors at sea by lowering and raising a ship's flag.
Directional light	A light illuminating a sector or very narrow angle and intended to mark a direction to be followed.
Dispatch boat	A vessel ranging in size from a small boat to a large ship tasked to carry military dispatches from ship to ship, from ship to shore, or, occasionally, from shore to shore.
Displacement	The weight of water displaced by the immersed volume of a ship's hull, exactly equivalent to the weight of the whole ship.
Displacement hull	A hull designed to travel through the water, rather than planing over it.
Disposable ship	Also drogher, raft ship, timber drogher, or timber ship. A barely seaworthy ship of the 19th century assembled from large timbers lashed or pegged together and designed to make a single voyage from North America to the United Kingdom and then to be disassembled so that her timbers could be sold, thus avoiding high British taxes on lumber imported as cargo. When British taxes on imported lumber fell, the construction of disposable ships ceased.
Disrate	To reduce in rank or rating; to demote.
Distinctive mark	A flag flown to distinguish ships of one seagoing service of a given country from ships of the country's other seagoing service(s) when ships of more than one of the country's seagoing services fly the same ensign.
Ditty bag	Bag or box for personal items.
Dock	1. In American usage, a fixed structure attached to shore to which a vessel is secured when in port, generally synonymous with pier and wharf, except that pier tends to refer to structures used for tying up commercial ships and to structures extending from shore for use in fishing, while dock refers more generally to facilities used for tying up ships or boats, including recreational craft. 2. In British usage, the body of water between two piers or wharves that accommodates vessels tied up at the piers or wharves.
Dockyard	A facility where ships or boats are built and repaired. Routinely used as a synonym for shipyard, although dockyard is sometimes associated more closely with a facility used for maintenance and basing activities, while shipyard sometimes is associated more closely with a facility used in construction.
Dodger	A hood forward of a hatch or cockpit to protect the crew from wind and spray. Can be soft or hard.
Dog
Dog watch	A short watch period, generally half the usual time (e.g., a two-hour watch rather than a four-hour one). Such watches might be included in order to rotate the system over different days for fairness, or to allow both watches to eat their meals at approximately normal times.
Doghouse	A slang term (in the US, mostly) for a raised portion of a ship's deck. A doghouse is usually added to improve headroom below or to shelter a hatch.
Dogvane	A small weathervane, sometimes improvised with a scrap of cloth, yarn, or other light material mounted within sight of the helmsman. See tell-tale.
Doldrums	The equatorial trough, with special reference to the light and variable nature of the winds generally encountered there. Also equatorial calms.
Dolly winch	A small winch mounted on the windlass, used as an alternative to the brails winch when that is obstructed in some way (e.g. by deck cargo).
Dolphin	A structure consisting of a number of piles driven into the seabed or riverbed as a marker.
Dolphin striker	A spar protruding vertically beneath a bowsprit, usually attached to the boswprit cap, used provide a mechanically advantageous run for the martingale stay, and other ropes of a ship's rigging.
Donkey engine	A small auxiliary engine used either to start a larger engine or independently, e.g. for pumping water on steamships.
Donkeyman	One of a ship's engineering crew. Often a crewman responsible for maintaining a steam donkey, or any machinery other than the main engines. On some ships, the Petty Officer in charge of engineroom ratings.
Dorade box	A dorade box (also called a dorade vent, collector box, or simply a "ventilator") is a type of vent that permits the passage of air in and out of the cabin or engine room of a boat while keeping rain, spray, and sea wash out.
Dory	A shallow-draft, lightweight boat, about 5 to 7 metres (16 to 23 ft) long, with high sides, a flat bottom, and sharp bows. Traditionally used as fishing boats, both in coastal waters and in the open sea. Also doree, dori, or (Royal Navy) dorey.
Double-banked	(of the arrangement of oars on a boat) having two oarsmen seated on each thwart, each of whom operates one oar on their side of the boat. This contrasts with single-banked, where only one oarsman is seated on each thwart operating one oar on one side of the boat, with the oars alternating between port and starboard along the length of the boat. A third arrangement is to have one rower on each thwart working two oars, one on each side of the boat.
Double-shotted	The practice of loading smoothbore cannon with two cannonballs.
Doubling the angle on the bow	A technique for establishing the distance from a point on land, such as a headland that is being passed. This is a type of running bearing which requires no plotting on the chart. The ship is sailed on a constant course and speed. The distance shown on the log is noted when the relative bearing of a fixed point is taken, and the increase in that bearing is watched until it is twice the original bearing, and the log is read again. The distance traveled between the two bearings is the distance of the ship from the fixed point when the second bearing was taken. Allowances for tidal streams may or may not be allowed for, depending on the accuracy required.
Dover cliffs	A slang term for very rough seas with large white-capped waves.
Downbound	1. Travel downstream, with a following current. 2. Eastward travel in the Great Lakes region (terminology used by the Saint Lawrence Seaway Development Corporation).
Downflooding
Downhaul	A line used to control either a mobile spar, or the shape of a sail. A downhaul can also be used to retrieve a sail back on deck.
Drabbler	An extra strip of canvas secured below a bonnet, further to increase the area of a course.
Draft	The depth of a ship's keel below the waterline. Also draught.
Dragger	1. A fishing trawler. 2. A dredger.
Dragon boat
Draught	Alternative spelling of draft.
Dreadnought	A type of battleship designed with an "all-big-gun" armament layout in which the ship's primary gun power resided in a primary battery of its largest guns intended for use at long range, with other gun armament limited to small weapons intended for close-range defense against torpedo boats and other small warships. Most, but not all, dreadnoughts also had steam turbine propulsion. Predominant from 1906, dreadnoughts differed from earlier steam battleships, retroactively dubbed predreadnoughts, which had only a few large guns, relied on an intermediate secondary battery used at shorter ranges for most of their offensive power, and had triple-expansion steam engines.
Dredger	A vessel specialized for use in the excavation of material from a water environment and equipped with heavy machinery for this purpose.
Dress overall	To string International Code of Signals flags, arranged at random, from stemhead to masthead, between mastheads (if the vessel has more than one mast), and then down to the taffrail, on a ship in harbor as a sign of celebration of a national, local, or personal anniversary, event, holiday, or occasion. When a ship is properly dressed overall, ensigns fly at each masthead unless displaced by another flag (e.g. that of a flag officer on board), in addition to the ensign flown in the usual position at the stern.
Dressing down	1. Treating old sails with oil or wax to renew them. 2. A verbal reprimand.
Dressing lines	Lines running from stemhead to masthead, between mastheads, and then down to the taffrail, to which flags are attached when a ship is dressed overall.
Drifter	A type of fishing boat designed to catch herring in a long drift net, long used in the Netherlands and Great Britain.
Drink	Overboard and into the water (e.g. "it fell into the drink").
Driver	The large sail flown from the mizzen gaff.
Driver-mast	The fifth mast of a six-masted barquentine or gaff schooner. It is preceded by the jigger mast and followed by the spanker mast. The sixth mast of the only seven-masted vessel, the gaff schooner Thomas W. Lawson, was normally called the pusher-mast.
Drogher	See disposable ship.
Drogue	A device to slow a boat down in a storm so that it does not speed excessively down the slope of a wave and crash into the next one. It is generally constructed of heavy flexible material in the shape of a cone. See also the sea anchor.
Drudging	A technique of maintaining steerageway when going downstream with neither engine nor wind to sail. The vessel uses its anchor to draw itself head-to-stream, then lifts the anchor and drifts stern-first downstream, ferry gliding to maintain position within the stream. As steerage begins to reduce, the vessel anchors again and then repeats the whole procedure as required.
Drydock	A narrow basin or vessel used for the construction, maintenance, and repair of ships, boats, and other watercraft that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform.
Drying harbor	A harbor where the water wholly or partly recedes as the tide goes out, leaving any vessel moored there aground. Also drying mooring.
Dunnage	1. Loose packing material used to protect a ship's cargo from damage during transport. See also fardage. 2. Personal baggage.
Dutch barge	Any of several types of traditional flat-bottomed shoal-draught sailing barge, originally used for carrying cargo in the Zuyder Zee and on the rivers of the Netherlands. Also schuyt.
Dutch built	Term of abuse implying shoddiness or (when directed at a person) stupidity or stubbornness, usually embellished with other oaths and insults tagged on fore and aft.
Dynamic Positioning	is a method to keep a ship, platform or subsea vehicle stationary over a fixed spot on the seafloor. Such station keeping is desirable for many tasks including coring, drilling, lifting, sampling and diver support. DP systems use thrusters in the bow and stern to maintain position. A computer is used to direct power to each thruster when necessary based upon input from GPS, compass , motion sensors, wind sensors, current meters , acoustic navigation equipment and other systems. More information on this subject may be found at http://www.imcaint.com/divisions/marine/reference/intro.html
Earings	Small lines by which the uppermost corners of the largest sails are secured to the yardarms.
East Indiaman	Any ship operating under charter or license to the East India Company (England), or to the Danish East India Company, French East India Company, Dutch East India Company, Portuguese East India Company, or Swedish East India Company from the 17th to the 19th centuries.
Echo Sounders	are used to measure water depth by sending an acoustic pulse to the seafloor and measuring how long it takes to be reflected back to the surface. Single beam echo sounders have a single transducer to transmit and receive sound. Multi-beam echo sounders have many transmit/receive hydrophones and thus cover a much larger area on the seafloor. This greater coverage makes it much quicker to survey a given area. Interferometry-based swath bathymetry survey systems offer wide-area, high-data-density coverage and are particularly suited to surveys in shallow coastal regions The term “interferometry” is generally used to describe swath-sounding sonar techniques that use the phase content of the sonar signal to measure the angle of a wave front returned from a sonar target. This technique may be contrasted with multibeam (and single beam) systems, which look for an amplitude peak on each beam in order to detect the sea-bed, or other targets, across the swath.
Echo sounding	The measurement of the depth of a body of water using a SONAR device. See also sounding and swinging the lead.
Embayed	A condition in which a sailing vessel (especially one that sails poorly to windward) is confined between two capes or headlands by a wind blowing directly onshore.
En echelon	An arrangement of gun turrets whereby the turret on one side of the ship is placed further aft than the one on the other side, so that both turrets can fire to either side.
Engine order telegraph	A communications device used by the pilot to order engineers in the engine room to power the vessel at a certain desired speed. Also chadburn.
Engine room	One of the machinery spaces of a vessel, usually the largest one, containing the ship's prime mover (usually a diesel or steam engine or a gas or steam turbine). Larger vessels may have more than one engine room.
Ensign	1. (flag) The principal flag or banner flown by a ship to indicate her nationality. 2. (rank) The lowest grade of commissioned officer in the U.S. Navy.
Environmental Engineering	In every coastal and offshore project, environmental sustainability is an important consideration for the preservation of ocean ecosystems and natural resources . Instances in which marine engineers benefit from knowledge of environmental engineering include creation of fisheries , clean-up of oil spills , and creation of coastal solutions . [28] ... (more at Environmental Engineering)
Escort carrier	A type of aircraft carrier, smaller and slower than a fleet carrier, used by some navies in World War II to escort convoys, ferry aircraft, and provide air support for amphibious operations.
Estimated position	An approximate geographical position obtained by making allowances for leeway, tide, and currents to a dead reckoning position (which is calculated from the distance run and the course steered).
Evaporator	A piece of ship's equipment used to produce fresh drinking water from sea water by distillation.
Executive officer	The officer second in command on a warship. Also called "X.O." in the United States and "Number One" in the Royal Navy and Commonwealth navies.
Extra ship
Extremis	The point under International Rules of the Road (Navigation Rules) at which the privileged (or stand-on) vessel on collision course with a burdened (or give-way) vessel determines it must maneuver to avoid a collision. Prior to extremis, the privileged vessel must maintain course and speed and the burdened vessel must maneuver to avoid collision. Also in extremis.
Eye splice
Factory ship	A large oceangoing vessel with extensive on-board facilities for processing and freezing caught fish or whales. Some also serve as mother ships for smaller fishing or whaling vessels. Those used for processing fish are also known as fish processing vessels.
Fair	1. A smooth curve, usually referring to a line of the hull with minimum localized deviations. 2. To make something flush.
Fairing	1. (n) A structure that improves the streamlining of a vessel. 2. (v) The process of making a curve or structure fair.
Fairlead	A device used to keep a line or chain running in the correct direction or to give it a fair lead to prevent it rubbing or fouling.
Fairleads, Chocks, Bitts, Bollards, Bilge And Dolphins	Fairleads, Chocks, Bitts, Bollards, Dolphins etc., are commonly used ship terms in mooring operations of vessels . ... (more at Fairleads, Chocks, Bitts, Bollards, Bilge And Dolphins)
Fairwater	1. A structure that improves the streamlining of a vessel. 2. On submarines: The superstructure (conning tower, sail,etc) of the boat.
Fairway	1. A navigable channel (e.g. in a harbor or offshore) that is the usual course taken by vessels in the area. 2. In military and naval terms, a channel from offshore, in a river, or in a harbor that has enough depth to accommodate the draft of large vessels.
Fake	A single turn of rope in a coil or on a drum. A group of fakes is known as a tier. See also fake down.
Fake down	To lay a coil of rope down so that it will run easily; that is, with rope feeding off the top of the coil and the bitter end at the bottom. Often confused with flake. See also range.
Falkuša	A traditional fishing boat with a lateen sail on a single mast used by fishermen from the town of Komiža on the Adriatic island of Vis.
Fall	The part of the tackle that is hauled upon.
Fall off	To change the direction of sail so as to point in a direction that is more downwind; to bring the bow leeward. This is the opposite of pointing up or heading up. Also bear down, bear away, bear off, or head down.
Fantail	The aft end of a ship, also known as the poop deck.
Fardage	Wood placed in the bottom of a ship to keep cargo dry. See also dunnage.
Fashion boards	Loose boards that slide in grooves to close off a companionway or cabin entrance.
Fast
Fathom	1. A unit of length equal to 6 feet (1.8 m), roughly measured as the distance between a man's outstretched hands. Particularly used in sounding as a measurement of the depth of a body of water. 2. To measure the depth of water; to engage in sounding.
Fathomer	A person engaged in sounding to determine the depth of water.
Fathometer	A depth finder that uses sound waves to determine the depth of water.
Favored side	The side of the course that gets you to the next mark faster, due to more wind, favorable shifts, less current, smaller waves, etc.
Felucca	A traditional wooden sailing boat with a rig consisting of one or two lateen sails, used in protected waters of the Red Sea and eastern Mediterranean and particularly along the Nile in Egypt and Sudan, as well as in Iraq.
Fend off	A command given to the crew to stop what they are now doing and to immediately manually prevent the boat from banging into the docks or other boats.
Fender	A flexible bumper used in boating to keep boats from banging into docks or each other. Often an old car tire.
Ferry	A merchant ship used to carry passengers, and sometimes vehicles and cargo, across a body of water. Also ferryboat.
Ferry glide	To hold a vessel against and at an angle to the current/stream such that the vessel moves sideways over the bottom due to the effect of the current operating on the upstream side of the vessel.
Ferry slip	A specialized docking facility designed to receive a ferryboat or train ferry.
Fetch	1. The distance across water a wind or waves have traveled. 2. To reach a mark without tacking.
Fid	1. A tapered wooden tool used for separating the strands of rope for splicing. 2. A bar used to fix an upper mast in place.
Fife rail	A freestanding pinrail surrounding the base of a mast and used for securing that mast's sails' halyards with a series of belaying pins.
Fifie	A sailing boat with two masts with a standard rig consisting of a main dipping lug sail and a mizzen standing lug sail. Developed in Scotland and used for commercial fishing from the 1850s until the 20th century.
Fight his ship	To fight his ship (or to fight her ship) is a naval term that denotes a captain taking his or her vessel into combat or directing his or her vessel in combat.
Fighting top	An enlarged top designed to allow gunfire downward onto an enemy ship. A fighting top could have small guns installed in it or could serve as a platform for snipers armed with muskets or rifles.
Figure of eight	A stopper knot.
Figurehead	A symbolic image, particularly a carved effigy, at the head of a traditional sailing ship or early steamer.
Fillet (welding)
Fin	A term used in European and British Commonwealth countries for a tower-like structure on the dorsal (topside) surface of a submarine; called a sail in the United States.
Fine	Narrow in appearance from the vantage point of a lookout or other person viewing activity in the vicinity of a ship, e.g. another ship off the starboard bow with her bow or stern facing the viewer's ship could be described as "fine on the starboard bow" of the viewer's ship.
Fire room	The compartment in which a ship's boilers or furnaces are stoked and fired. Also boiler room.
Fire ship	A ship loaded with flammable materials and explosives and sailed into an enemy port or fleet either already burning or ready to be set alight by its crew (who would then abandon it) in order to collide with and set fire to enemy ships.
Fireboat	A specialized vessel equipped with firefighting equipment such as pumps and nozzles for fighting shipboard and shoreline fires.
Fireman	Also stoker, boilerman, or watertender. 1. A job associated with tending the fire for a boiler.
First mate	The second-in-command of a commercial ship.
First-rate	The classification for the largest sailing warships of the 17th through the 19th centuries. Such vessels often had up to three masts, 850+ crew, and 100+ guns.
Fish	1. To repair a mast or spar with a fillet of wood. 2. To secure an anchor on the side of a ship for sea (otherwise known as "catting".)
Fisherman's reef	A sailing tactic for handling winds too strong for the sail area hoisted when reefing the sails is not feasible or possible. The headsail is set normally while the mainsail is let out until it is constantly luffing. This creates a loss of force on the main and also reduces the efficiency of the headsail while still retaining sailing control of the vessel.
Fisherman's sail	On a staysail schooner, the fisherman is a quadrilateral sail set between the two masts above the main staysail. It is used in light to moderate airs.
Fitting-out	The period after a ship is launched during which all the remaining construction of the ship is completed and she is readied for sea trials and delivery to her owners.
Fixed propeller	A propeller mounted on a rigid shaft protruding from the hull of a vessel, usually driven by an inboard motor; steering must be done using a rudder. See also outboard motor and sterndrive.
Flag hoist	A number of signal flags strung together to convey a message, e.g. "England expects that every man will do his duty".
Flag of convenience	The business practice of registering a merchant ship in a sovereign state different from that of the ship's owners, and flying that state's civil ensign on the ship. The practice allows the ship's owner to reduce operating costs or avoid the regulations of the owner's country.
Flag officer	1. A commissioned officer senior enough to be entitled to fly a flag to mark the ship or installation under their command, in English-speaking countries usually referring to the senior officers of a navy, specifically to those who hold any of the admiral ranks and in some cases to those holding the rank of commodore. In modern American usage, additionally applied to U.S. Coast Guard and National Oceanic and Atmospheric Administration Commissioned Corps officers and general officers in the U.S. Army, U.S. Air Force, and U.S. Marine Corps entitled to fly their own flags. 2. A formal rank in the mid-19th century U.S. Navy, conveyed temporarily upon senior captains in command of squadrons of ships, soon rendered obsolete by the creation of the ranks of commodore and rear admiral.
Flake	To set down in folds, as in stowing a sail or to range a cable on deck so that it is clear to run. Not to be confused with fake down.
Flank	The maximum speed of a ship. Faster than "full speed".
Flare	1. A curvature of the topsides outward towards the gunwale. 2. A pyrotechnic signaling device, usually used to indicate distress.
Flatback	A Great Lakes slang term for a vessel without any self-unloading equipment.
Flatboat	A rectangular, flat-bottomed boat with square ends used to transport freight and passengers on inland waterways in the United States during the 18th and 19th centuries. Also broadhorn.
Flattop	A slang term for an aircraft carrier.
Fleet	1. Naval fleet: The highest operational echelon of command of ships commanded by a single person in a navy, and typically the largest type of naval formation commanded by a single person. In modern times, usually (but not necessarily) a permanent formation. 2. During the Age of Sail, a Royal Navy term for any naval command larger than a squadron in size, or commanded by a rear admiral and composed of five ships-of-the-line and any number of smaller vessels.
Flemish	To coil a line that is not in use so that it lies flat on the deck.
Flettner rotor	A spinning cylinder that uses the Magnus effect to harness wind power to propel a ship.
Flight deck	A flat deck on an aircraft carrier used for the launch and recovery of aircraft. In the United States Navy, the term flight deck also refers to a helicopter deck.
Flog the glass	The act of vibrating or shaking a half-hour marine sandglass — used until the early 19th century to time the length of a watch — to speed the passage of the sand in order to get off watch duty earlier.
Floor	The transverse structural timbers to which the longitudinal bottom planking is attached. The equivalent side timbers are called the frames. The keelson is fastened on top of the floors, bolting them to the keel. The planking is the exterior of the hull, while the ceiling is attached on top of the floors, and it forms the base of the hold.
Floorhead	Any of the upper extremities of the floor of a vessel.
Floors	They are a part of the frames in the bottom structure, ideally from the keel to the bilge strake level. Floors have higher scantlings than the part of the frame on the side shells. They usually stiffen the bottom shell plating against lateral loads and, for double bottom constructions, also help support the inner bottom plating. Floors are generally of two types, solid floors and bracket floors.
Flotation	: In marine technology, flotation can be divided into materials intended for use on the surface and those for use underwater. For surface flotation, buoys are fabricated out of steel or other metals, molded plastic or plastic foams. Ionomer foam is a popular material because of its reduced weight and high durability. Underwater, subsea flotation is often needed to achieve neutral buoyancy for subsea vehicles and platforms or to provide a positively buoyant upward force. Because of the compressive force of water pressure, subsea flotation is a more challenging problem then it is on the surface. ... (more at Flotation)
Flotilla	1. In naval usage, a group of warships under a single commander that is smaller than a fleet but otherwise not formally defined. A flotilla often is larger than a squadron, and usually is made up of smaller vessels than those assigned to a squadron, but some flotillas are smaller than squadrons and some include larger vessels. In some navies, the term flotilla is reserved for naval formations that operate on inland bodies of water, while the terms fleet and squadron denote naval formations that operate at sea. A flotilla may be a permanent or temporary formation. In modern times, a flotilla is sometimes an administrative naval unit responsible for maintaining and supporting vessels but not for commanding their operations at sea. 2. Informally, a group of naval or civilian vessels operating together or in close proximity to one another.
Flotilla holiday	A group of chartered yachts that set out together on the same route.
Flotilla leader	A warship suitable for commanding a flotilla of destroyers or other small warships, typically a small cruiser or a large destroyer, in the latter case known as a destroyer leader.
Flotsam	Debris or cargo that remains afloat after a shipwreck. See also jetsam.
Fluke	The wedge-shaped part of an anchor's arms that digs into the solid bottom beneath a body of water.
Flush deck	An upper deck of a vessel that extends unbroken from stem to stern.
Flush decker	1. Any vessel with a flush deck. 2. A U.S. Navy destroyer of the World War I-era Caldwell, Wickes, or Clemson class, produced in very large numbers.
Flushing board	A board inserted vertically in a cabin entrance.
Fluyt	A Dutch transoceanic sailing cargo vessel, square-rigged with two or three masts that were much taller than the masts of a galleon, developed in the 16th century and widely used in the 17th and 18th centuries. Also fluit or flute.
Fly by night	A large sail used only for sailing downwind, requiring little attention.
Folding propeller	A propeller with folding blades, furling so as to reduce drag on a sailing vessel when not in use.
Following sea	Waves going in the same direction as a ship, or within 15° of the heading, at a speed slower than the ship. See overtaking sea for waves traveling faster than the ship.
Foo-foo band	An impromptu musical band on late 19th-century sailing vessels, made up from members of the ship's crew.
Foot	1. The lower edge of any sail. 2. The bottom of a mast.
Footboat	A barge's boat or dinghy.
Footloose	If the foot of a sail is not secured properly, it is footloose, blowing around in the wind. Also, a classic Kevin Bacon film from early in his career.
Footrope	Each yard on a square-rigged sailing ship is equipped with a footrope for sailors to stand on while setting or stowing the sails.
Force	See Beaufort scale.
Fore	Toward the bow of a vessel. Also forward (often written as for'ard).
Fore horse	A transverse wooden or iron beam afore the main mast to which the foresail sheet is attached.
Fore-and-aft rig	A sailing rig consisting mainly of sails that are set along the line of the keel rather than perpendicular to it. Such sails, and the vessel itself, are said to be fore-and-aft-rigged.
Fore-and-afters	Removable wooded beams running along the center of the hold openings, beneath the hatches that they support.
Forecastle	(pronounced /ˈfoʊksəl/) A partial deck above the upper deck and at the head of the vessel; traditionally the location of the sailors' living quarters. The name is derived from the castle fitted to bear archers in time of war.
Foredeck	The portion of the deck that is forward of the forward mast.
Forefoot	The lower part of the stem of a ship.
Forehold	The forward (i.e., front) part of a hold.
Foremast jack	An enlisted sailor, one who is housed before the foremast.
Forepeak	The part of the hold of a ship within the angle of the bow.
Foresail	1. A fore-and-aft-rigged sail set on the foremast. 2. The lowest sail set on the foremast of a full-rigged ship or other square-rigged vessel.
Forestay	A long line or cable reaching from the bow of the vessel to the mastheads, used to support the mast.
Forestaysail	A triangular sail set on the forestay.
Foul	1. Having freedom of motion interfered with by collision or entanglement; entangled; the opposite of clear. For instance, a rope is foul when it does not run straight or smoothly, and an anchor is foul when it is caught on an obstruction. 2. A ship′s bottom is foul when it is overgrown with marine life such as barnacles.
Foulies	A slang term for oilskins, the foul-weather clothing worn by sailors.
Founder	To fill with water and sink.
Four piper	A term sometimes used to refer to United States Navy four-funneled destroyers of the Bainbridge, Paulding, Wickes, and Clemson classes, all built for service in World War I.
Frame	A transverse structural member that gives the hull strength and shape. Wooden frames may be sawn, bent, or laminated into shape; planking is then fastened to the frames. A bent frame is called a timber.
Frames	The transverse structural members run from the keel to the deck edge at the main deck level. They are usually perpendicular to the outer shell plating and transversely stiffen the outer side shell and outer bottom plating.
Freeboard	The height of a ship's hull (excluding the superstructure) above the waterline; the vertical distance from the current waterline to the lowest point on the highest continuous watertight deck. This usually varies from one part to another.
Freeing ports
Freighter	A cargo ship.
Frigate	1. In the 17th century, any warship built for speed and maneuverability. 2. In the 18th and early 19th centuries, a sailing warship with a single continuous gun deck, typically used for patrolling, blockading, etc., but not in line of battle.
Full and by	Sailing into the wind (by), but not as close-hauled as might be possible, so as to make sure the sails are kept full. This provides a margin for error to avoid being taken aback in a tricky sea (a serious risk for square-rigged vessels). Figuratively it implies getting on with the job but in a steady, relaxed way, without undue urgency or strain.
Full steam ahead	With as much speed as possible.
Full-rigged ship	A sailing vessel with three or more masts, all of them square-rigged. A full-rigged ship is said to have a "ship rig".
Funnel	1. (funnel) Also stack. The smokestack of a ship, used to expel boiler steam and smoke or engine exhaust. 2. Ventilation funnel: A curved, rotatable tube protruding from the deck of a vessel, designed to direct fresh air into her interior.
Furious Fifties	Strong westerly winds found in the Southern Hemisphere, generally between the latitudes of 50 and 60 degrees. They are stronger than the similar "Roaring Forties" to their north.
Furl	To roll or gather a sail against its mast or spar.
Furnace	Boiler component where fuel is burned.
Fuse Panel
Fusta	A narrow, light, and fast ship with a shallow draft, powered both by oars and sail, with a single mast carrying a lateen sail; a favorite of North African corsairs during the 16th and 17th centuries. Also fuste, foist, or galliot.
Futtock shrouds	Rope, wire, or chain links in the rigging of a traditional square-rigged ship running from the outer edges of a top downwards and inwards to a point on the mast or lower shrouds. They carry the load of the shrouds that rise from the edge of the top, preventing the top from tilting relative to the mast.
Futtocks	Pieces of timber that make up a large transverse frame.
GPS	(Global Positioning System): Users of a global positioning system can calculate their location anywhere on the earth. Two “public” GPS systems are The NAVSTAR system, owned by the United States and managed by the Department of Defense, and the GLONASS system, owned by the Russian Federation. Global Positioning Systems are space-based radio positioning systems that provide 24-hour, three-dimensional position, velocity and time information to suitably equipped users anywhere on the surface of the Earth. The GPS signals do not penetrate through water, so subsea vehicles must surface to get a GPS fix. The system works by a constellation of satellites that transmit timing information, satellite location information and satellite health information. The user requires a special radio receiver – a GPS receiver – to receive the transmissions from the satellites. The GPS receiver contains a specialized computer that makes calculations based on the satellite signals. The user gets 24-hour, three-dimensional position, velocity and time information and does not have to transmit anything to the satellite. ... (more at GPS)
Gaff	1. (gaff rig) A spar that holds the upper edge of a four-sided fore-and-aft-mounted sail. On a hoisting gaff, the lower end is supported by gaff jaws which partly encircle the mast; it is hoisted using peak and throat halliards. A standing gaff remains aloft, its sails brailed when not in use 2. (fishing gaff) A hook on a long pole used to haul in fish.
Gaff rig	A boat rigged with a four-sided fore-and-aft sail set abaft the mast, its head being spread by a gaff. The gaff may be standing (permanently in position) with the sail being brailed up to the gaff when not in use, or, more commonly, is hoisted using two halliards: the peak and the throat.
Gaff topsail	A fore-and-aft sail set above a gaff-rigged sail, with the clew sheeted to the end of the gaff.
Gaff vang	A line rigged to the end of a gaff and used to adjust a gaff sail's trim.
Gale	See ghali.
Gali	See ghali.
Galleass	1. An oared warship of the 16th century equipped with a gun deck; larger and equipped with more sails than a galley. 2. A flat-bottomed commercial sailing vessel of the North Sea and western Baltic Sea.
Galleon
Galley	1. (galley (kitchen)) The compartment of a ship where food is cooked or prepared; a ship's kitchen. 2. (galley) A type of ship propelled by oars, used especially in the Mediterranean for warfare, piracy, and trade from the 8th century BC to the 16th century AD, with some in use until the early 19th century.
Galliot	See fusta.
Gam	A meeting of two (or more) whaling ships at sea. The ships each send out a boat to the other, and the two captains meet on one ship, while the two chief mates meet on the other.
Gammon iron	The bow fitting that clamps the bowsprit to the stem.
Gangplank	A movable bridge used in boarding or leaving a ship at a pier. Also brow.
Gangway	An opening in the bulwark of a ship to allow passengers to board or leave the ship.
Gangway And Accommodation Ladders	These are still the two most often interchanged ship terms used on vessels. Although, their purpose is the same. i.e. to serve as a link/bridge between the ship and the shore, their rigging and usage are different. ... (more at Gangway And Accommodation Ladders)
Gantline	A rope running through a block at or near the masthead, with both ends reaching the deck. It is used solely for hoisting and lowering crew members and/or tools into the rigging for maintenance and repair work.
Garbling	The illegal practice of mixing cargo with garbage.
Garboard	The strake closest to the keel (from Dutch gaarboard).
Garboard planks	The planks immediately on either side of the keel.
Gash	Any refuse or rubbish discarded into a refuse container or dustbin, also known as "gash fanny" (South African Navy).
Gasket	A rope used to secure a sail (particularly the topsail) when stowed.
Gate ship	An alternative term for a net-laying ship.
Gear	A collective term for a vessel's sails and rigging.
Geedunk	Ice cream, snacks, etc. Also the place selling such items.
General quarters	See battle stations.
Gennaker	A large, lightweight sail used for sailing a fore-and-aft rig down or across the wind, intermediate between a genoa and a spinnaker.
Genoa	A large jib, strongly overlapping the mainmast. Also genny. (both /ˈdʒɛni/)
Geophysical Instruments	are used by scientists and those seeking hard minerals and hydrocarbon deposits to study those parts of the earth hidden from direct view. Instruments used underwater include magnetometers (which are described in this glossary under their own listing), gravimeters, and seismometers. Seismic devices are another class of underwater geophysical equipment used to generate shock waves so reflected signals can be used to detect structures under the sea floor. Dynamite was originally used to generate shock waves. Today mechanical devices such as air guns, bubble pulsers, boomers and sparkers are utilized. The reflected signals are detected by hydrophones that can either be placed on the seafloor or towed behind a ship. Streamer cables are arrays of hydrophones that are wired together and contained in oil-filled plastic hose. ... (more at Geophysical Instruments)
Ghali	Any of several types of galley-like ships from the Nusantara archipelago in Southeast Asia. The term refers both to Mediterranean vessels built by local people and to native vessels with Mediterranean influence. Also gali or gale.
Ghost	To sail slowly when there is apparently no wind.
Ghost fleet	In the modern United States, an informal term for a reserve fleet.
Gibe	See gybe.
Gig	A type of open boat designed primarily for propulsion under oar, but often fitted with a sailing rig for appropriate conditions. Used most often for the swift transport of one or a few people, as in a pilot gig or as a naval ship's boat. In U.S. Navy usage, a captain's gig is reserved for use by a ship's captain and, in modern times, is a power-boat.
Gillnetter	A fishing vessel that employs gillnetting as its means of catching fish.
Gin-pole	A pole that is attached perpendicular to a mast, to be used as a lever for raising the mast. Also jin-pole.
Girders	Girders are heavy scantling longitudinal stiffeners situated at the bottom, sides, and deck, with greater dimensions than longitudinal. Large bars, I-beams, or high scantling L-sections are placed at definite intervals between longitudinals in the top and bottom structure. The keel is often a girder of high dimensions.
Girt	1. Said of a vessel moored by cables to two anchors in such a way that the force of a current or tide causes her to swing against one of the cables. 2. To capsize because of forces exerted on a cable by another vessel attached to it. Tug girting specifically refers to girting that causes a tugboat to capsize because of forces placed on a cable attached to her by another vessel attached to the same cable.
Give-way	In a situation where two vessels are approaching one another so as to involve a risk of collision, the vessel is directed to keep out of the way of the other.
Glass	1. A marine barometer. Older barometers used mercury-filled glass tubes to measure and indicate barometric pressure. 2. A marine sandglass.
Global Positioning System (GPS)	A satellite-based radionavigation system providing continuous worldwide coverage of geolocation and time information to air, marine, and land users wherever there is an unobstructed line of sight to at least four GPS satellites developed and operated by the United States Department of Defense but publicly available for use by anyone with an enabled GPS receiver.
Go-fast boat	A small, fast boat designed with a long narrow platform and a planing hull to enable it to reach high speeds. Colloquially equivalent to a "rum-runner" or a "cigarette boat".
Goat locker	A mess hall reserved for chief petty officers in the United States Navy.
Going about	Changing from one tack to another by going through the wind. See also gybe.
Gondola	1. A traditional, flat-bottomed Venetian rowing boat. 2. An alternative term for a gundalow.
Gooseneck	A fitting that attaches a boom to a mast yet allows it to move freely.
Goosewinged	Goosewing (of a fore-and-aft-rigged vessel) Sailing directly away from the wind, with the sails set on opposite sides of the vessel (e.g. with the mainsail to port and the jib to starboard) so as to maximize the amount of canvas exposed to the wind. See also running.
Grave	To clean a ship's bottom.
Graving dock	A narrow basin, usually made of earthen berms and concrete, closed by gates or by a caisson, into which a vessel may be floated and the water pumped out, leaving the vessel supported on blocks; the classic form of drydock.
Graybeard	See Cape Horn roller.
Grease  gang	The engineering crew of the vessel, i.e. crew members who work in the vessel's engine room, fire room and/or boiler room, so called because they would typically be covered in coal dust during the days of coal-fired steamships.
Great-circle navigation	The practice of navigating a vessel along the arc of a great circle. Such routes yield the shortest possible distance between any given pair of points on the surface of the Earth.
Green water	1. That portion of the ocean lying generally within a few hundred nautical miles of shore but beyond the edge of the continental shelf, and thus between "brown water" over the continental shelf and "blue water" farther out to sea. 2. A large amount of water on or passing over or across a ship's deck or superstructure after a large wave strikes her, e.g., The ship took green water over her bow during the storm.
Green-to-green	A passage of two vessels moving in the opposite direction on their starboard sides, so called because the green navigation light on one of the vessels faces the green light on the other vessel.
Green-water navy	A navy capable of sustained operations beyond coastal areas out to a few hundred nautical miles from shore, i.e., in "green water," but not farther into the open ocean, i.e., in "blue water." While a green-water navy can possess ships capable of operating farther out to sea than in "green water," it requires logistical support from foreign countries to sustain such longer-range operations.
Greenlandman	A British term used in the 18th and 19th centuries for any whaling ship operating in the Arctic Ocean or northern waters near the Arctic.
Gridiron	A large metal cross-frame on which vessels are placed at high water for examination, cleaning, and repairs after the tide falls.
Gripe	A temporary eye in a line (rope).
Gripie	A Cockney (London dialect) name for a barge.
Griping	The tendency of a ship to turn into the wind despite the efforts of the helmsman, usually due to either the design of a ship or more commonly the incorrect distribution of weight on and within the hull.
Grog
Groggy	Drunk from having consumed a lot of grog.
Grommet	1. A metal or plastic ring inserted in canvas to prevent wear. 2. A ring of rope.
Ground	The bed of the sea; the underwater surface or sea floor to which an anchor holds.
Grounding	When a ship (while afloat) touches the bed of the sea, or runs aground. A moored vessel that grounds as the tide goes out is said to "take the ground".
Groundway	A substantial foundation of wood or stone for the blocks on which a vessel is built, typically lying on either side of the keel of a ship under construction, which also serves to support and guide the blocks when they slide to carry the vessel into the water when she is launched. Also ground way.
Growler	A small iceberg or ice floe barely visible above the surface of the water.
Guard ship	1. Any vessel that makes the rounds of a fleet at anchor to see that due watch is kept at night. 2. A warship stationed at a port or harbor to act as a guard there.
Guards	Also paddle guards and wheel guards. 1. (on an oceangoing sidewheel steamship) Horizontal structures, usually of wood, built around the paddle boxes just above their lowest point and extending a short distance forward and aft, designed to protect them from damage and to provide additional support for the paddle shaft.
Guineaman	Another name for a slave ship, coined after the emergence of the transatlantic slave trade from Africa in the 15th century.
Gulf and Bay	The world’s waterbodies are divided into Oceans, Seas, Gulfs, Bays, Rivers, Estuaries, Lakes, Straits, Canals etc. Most of these are self-explanatory. However, most people fail to understand the difference between Gulf and Bay and Straits, Channels and Canals. ... (more at Gulf and Bay)
Gun deck	1. Up through the 19th century, a deck aboard a ship that was primarily used for the mounting of cannon to be fired in broadsides. 2. On smaller vessels (of frigate size or smaller) up through the 19th century, the completely covered level under the upper deck, though in such smaller ships it carried none of the ship's guns.
Gundalow	A type of flat-bottomed sailing barge with a single large lateen sail brailed to a heavy yard, used on rivers in Maine and New Hampshire from the mid-17th century to the early 20th century. Sometimes referred to as a gondola in period accounts.
Gundecking	Falsifying of records and reports.
Gunner's daughter	See kissing the gunner's daughter.
Gunport	An opening in the side of a ship or in a turret through which a gun fires or protrudes.
Gunter rig	A fore-and-aft sail set abaft (behind) the mast, approximately triangular in shape, with the top half of the luff (front) of the sail attached to a yard which extends the sail above the top of the mast. The yard is raised and lowered with the sail. This traditional sail is popular in small boats and produces aerodynamic performance close to that of the highly developed Bermuda rig. Also sliding gunter or gunter lug.
Gunwale	Generally, the upper edge of the hull; more specifically, in an open (undecked) boat of timber construction, the longitudinal stringer that connects the top of the ribs. Rarely gunnel. (both /ˈɡʌnəl/)
Gurdy	A mechanical crank used to set and retrieve fishing lines.
Guy	1. A rope or stay leading to the side of the vessel. 2. A rope used to steady a boom.
Gypsy winch	A type or component of an anchor winch. The "gypsy" or "gypsy wheel" engages the anchor chain.
HVSC	High Voltage Shore Connection
Half-breadth plan	In shipbuilding, an elevation of the lines of a ship, viewed from above and divided lengthwise.
Halyard	Originally, ropes were used for hoisting a spar with a sail attached; today, a line is used to raise the head of any sail. Also halliard.
Hammock	Canvas sheets, slung from the deckhead in mess decks, in which seamen slept. "Lash up and stow" was a piped command to tie up hammocks and stow them (typically) in racks inboard of the ship's side so as to protect the crew from splinters from shot and provide a ready means of preventing flooding caused by damage.
Hamper	Articles that normally are indispensable aboard ship but at certain times are in the way.
Hand	To furl a sail.
Hand bomber	A ship using coal-fired boilers shoveled in by hand.
Hand over Fist	To climb steadily upwards, from the motion of a sailor climbing shrouds on a sailing ship (originally "hand over hand").
Handsomely	With a slow even motion, as when hauling on a line "handsomely".
Handy billy	A loose block and tackle with a hook or tail on each end, which can be used wherever it is needed. Usually made up of one single and one double block.
Hangar deck	An enclosed deck on an aircraft carrier, usually beneath the flight deck and intended for use as a hangar in servicing and storing aircraft.
Hank	A fastener attached to the luff of the headsail that attaches the headsail to the forestay. Typical designs include a bronze or plastic hook with a spring-operated gate, or a strip of cloth webbing with a snap fastener.
Harbor
Harbor dues	The fees charged by the owners or operators of a harbor to those vessels using the harbor. Under British legislation, the person in charge of a vessel must report to the harbourmaster within 24 hours of arrival in a port where harbor dues are payable.
Harbor of refuge	An artificial harbor constructed on a coast without a natural harbor to provide shelter for small vessels.
Harbourmaster	A person in charge of a harbor, with powers including the collection of the harbor dues, instructing the masters of vessels where to moor, and overall safety within the area of the harbor, often including pilotage and navigational aids. In most countries the powers of a harbor master are laid down by legislation, and can be quite extensive.
Hard	A section of otherwise muddy shoreline suitable for mooring or hauling out.
Hard-a-lee	See lee-oh.
Harden in	To haul in the sheet and tighten the sails.
Harden up	To turn towards the wind; to sail closer to the wind.
Hardtack	A hard and long-lasting dry biscuit, used as food on long journeys. Also called a "ship's biscuit".
Harness cask	A large, usually round tub lashed to a vessel's deck containing dried and salted provisions for daily use. Also harness tub.
Hatches	Hatches are nothing but covers on openings at various deck levels for the access of men, cargo, or other items. These are also stiffened and of a specific strength to compensate for the loss of strength on deck structures due to the openings or cut-outs. They may be watertight or non-watertight.
Hatchway	A covered opening in a ship's deck through which cargo can be loaded or access made to a lower deck; the cover to the opening is called a hatch. Also hatch.
Haul	1. To steer (a vessel) closer to the direction of the wind. 2. To shift forward, i.e. more toward the bow of the vessel.
Hauling wind	Pointing the ship towards the direction of the wind; generally not the fastest point of travel on a sailing vessel.
Hawsepipe	The shaft or hole in the side of a vessel's bow through which the anchor chain passes. "In through the hawse pipe" describes someone with experience and savvy. Also hawsehole or hawse.
Hawsepiper	An informal term for an officer of a merchant ship who began their career as an unlicensed merchant seaman, and so did not attend a traditional maritime academy to earn their officer's license. See also before the mast.
Hawser
Head	1. The forwardmost or uppermost portion of the ship. 2. The forwardmost or uppermost portion of any individual part of the ship, e.g. masthead, beakhead, stemhead, etc.
Head boat	A fishing boat that takes recreational fishermen out for a fee paid individually by each person (i.e. per head). A head boat differs from a charter boat, which is a fishing boat that a party of fishermen hires for an agreed-upon period.
Head of navigation	The farthest point above the mouth of a river that can be navigated by ships.
Head rail	A curved rail that extends from the figurehead to the bow of a ship.
Head rope	1. The mooring rope that goes from the bow of a vessel to a point on a jetty a distance ahead of the bows. 2. Part of the bolt rope, at the head of a sail, running from the mast to the spirit.
Head sea	A sea in which waves are directly opposing the motion of the ship, or approaching within 15° of ahead.
Head-sail	1. Jibs and staysails are set between the bowsprit and the fore. 2. Sometimes refers to the square sails on the fore-mast of a square rigged vessel.
Head-stays	Stays between the bowsprit and the foremost mast.
Header	A change in the wind direction that forces the helmsman of a close-hauled sailboat to steer away from its current course to a less favorable one. This is the opposite of a lift.
Heading	The direction in which the nose of a vessel is pointing (which is not necessarily the same as the direction in which the vessel is actually moving).
Headsail	Any sail set in front of the most forward mast. A sailing vessel may have one or more headsails. A headsail may be hanked to a stay, or may be set flying, with the luff being kept taut by the tension of the halyard. Where several headsails are set, a complex arrangement might be termed (from the front and top) flying jib, outer jib, inner jib, and (fore) staysail; less complex would be jib and staysail.
Heat Exchangers
Heave	A vessel's transient, vertical, up-and-down motion.
Heave down	To turn a ship on its side (for cleaning), a process which is also known as careening.
Heave ho!	An exclamation sailors make when pulling forcefully on a rope.
Heave to	See hove to.
Heavy weather	A combination of high winds and rough seas that may be dangerous for a ship or boat, sometimes requiring changes to a passage plan (such as a precautionary diversion to a safe harbor), heaving to, running under bare poles, or other similar survival strategies.
Heel	1. The lean caused by the wind's force on the sails of a sailing vessel. 2. The inclination or canting of a vessel to one side or the other from the vertical as she maneuvers, e.g. "The ship heeled to port as she turned to starboard".
Helicopter deck	A helicopter pad on the deck of a ship. In the United States Navy, a helicopter deck is referred to as a flight deck.
Helm	1. A ship's steering mechanism, such as a tiller or ship's wheel. 2. The wheel and/or wheelhouse area.
Helmsman	A member of the crew who is responsible for steering the ship. Also steersman.
Herring buss	A type of seagoing fishing vessel used by Dutch and Flemish herring fishermen from the 15th through the early 19th century.
Highfield lever	A type of tensioning lever, usually for running backstays. Their use allows the leeward backstay to be completely slackened so that the boom can be let fully out.
Hitch	A knot used to tie a rope or line to a fixed object. See also bend.
Hobby horsing	Harmonic pitching of a vessel forward and backward.
Hog	1. A fore-and-aft structural member of the hull fitted over the keel to provide a fixing for the garboard planks. 2. A rough, flat scrubbing brush for cleaning a ship's bottom underwater.
Hog Islander
Hog frame	A heavy wooden truss fitted lengthwise along each side of a large American steamboat, secured to the hull and rising above deck just outside the superstructure, to provide support for the hull and prevent hogging. Similar in appearance and function to a truss bridge. See also the king post.
Hogging	2. A permanent distortion of the hull in the same manner as above, caused over time by the bow and stern of a ship being less buoyant than the midships section. During the Age of Sail, shipwrights employed a number of different designs of braces to stiffen ships' hulls against this warping.
Hogging line	A line passed under a ship from side to side to pull a collision mat into place over a leak. Also a line passed under a ship from side to side used as a reference to indicate position of a frame during underwater inspections.
Hoist	The height of a fore-and-aft-rigged sail as measured next to the mast or stay.
Hold	The lower part of the interior of a ship's hull, especially when considered as storage space, as for cargo. In earlier use, the term referred to all interior spaces below the orlop deck; in later merchant vessels it extended up through the decks to the underside of the weather deck.
Holiday	A gap in the coverage of newly applied paint, slush, tar, or another preservative.
Holystone	A chunk of sandstone used to scrub a ship's decks. The name comes from both the kneeling position sailors adopt to scrub the deck (reminiscent of genuflection for prayer), and the stone itself (which resembled a Bible in shape and size).
Home port	The port at which a vessel is based. Often confused with the ship's port of registry, which is the port listed in the vessel's registration documents and lettered on her stern but which may differ from her home port. In the cruise ship industry, the term "home port" is often incorrectly used to refer to a ship's port of departure.
Homeward bounder	A slang term for a sail repair, especially one done with large herringbone stitches.
Honey barge	Slang term for a vessel that transports sewage.
Hoop	Wooden or metal hoops are used to secure the topsail to the topmast so it can be speedily raised or lowered.
Horn	A sound signal that uses electricity or compressed air to vibrate a disc diaphragm.
Horn timber	A fore-and-aft structural member of the hull sloping up and backwards from the keel to support the counter.
Hornpipe	A type of dance.
Horns	Shaped ends to the chocks where the main horse is bolted.
Horse	1. A metal bar (sometimes a shaped aluminum extrusion), running athwartships, to which a sheet is attached with a traveler that slides along the horse or is adjusted to be fixed in one position on it. Commonly used for a mainsheet, but also seen with some headsails, particularly a staysail fitted with a boom. 2. Sand lying mid-channel.
Horse latitudes	The latitudes between 30 and 35 degrees in the Northern Hemisphere and between 30 and 35 degrees in the Southern Hemisphere in which weather patterns often result in sailing vessels being becalmed in mid-ocean.
Hospital ship	A ship designated and equipped to serve primarily as a floating medical healthcare facility or hospital, usually operated by military forces such as navies for use in or near war zones, or for the support of disaster relief and other humanitarian operations.
Hotel load	The electrical load for all non-propulsion systems on a ship, including lighting, climate control, and services used by the crew and passengers.
Hounds	Attachments of stays to masts.
Hove to	1. In a sailing vessel, stopping her by backing some of the sails and lashing the helm to leeward. In a fore-and-aft-rigged sloop, this involves backing the headsail and allowing the mainsail to fill somewhat (the precise arrangement varies from one vessel to another). The vessel will gradually drift to leeward, with the speed of the drift depending on the vessel's design. 2. In a powered vessel, stopping her by stopping her engines.
Hoveller	1. Someone who does salvage work, such as that done by Deal boatmen. 2. An additional crewman who assists getting a vessel in and out of harbor. See also huffler (regional usage of these words varies substantially, with strongly held views on the differences).
How's your head?	A question asked of the helmsman to report the vessel's course at that moment. The actual course may differ from the course to steer that has been ordered.
Hoy	2. A barge making regular passages on a fixed route with mixed third-party cargoes. Also passage barge or goods barge.
Hufflers	Additional crew taken on to enter harbor or navigate in confined waters, particularly applying to Thames barges. See also hoveller.
Hulk	1. A ship, often an old ship or one that has become obsolete or uneconomical to operate, that has had its rigging or internal equipment removed and is incapable of going to sea, but that is still afloat and continues to serve a useful function, such as providing living, office, training, storage, or prison space. 2. (v.) To convert a ship into a hulk.
Hull	The shell and framework of the basic flotation-oriented part of a ship.
Hull speed	The maximum efficient speed of a displacement-hulled vessel.
Hull-down	Of a vessel when only her upper parts (e.g. funnel, masts, and superstructure) are visible on the horizon but her hull remains below the horizon. Contrast hull-up.
Hull-up	Of a vessel when her hull as well as her upper parts (e.g., funnel, masts, and superstructure) are visible on the horizon. Contrast hull-down.
Hydrodynamic loading	In the same way that civil engineers design to accommodate wind loads on building and bridges, marine engineers design to accommodate a ship or submarine struck by waves millions of times over the course of the vessel's life. ... (more at Hydrodynamic loading)
Hydrofoil	A boat with wing-like foils mounted on struts below the hull, lifting the hull entirely out of the water at speed and therefore greatly reducing water resistance.
Hydrophones	: Underwater hydrophones detect acoustic signals in the ocean just as microphones collect sound in the air. Most hydrophones are based on a special property (piezoelecticity) of certain ceramics that produce a small electrical current when subjected to pressure changes. When submerged in water, a ceramic hydrophone produces smallvoltage signals over a wide range of frequencies as it is exposed to underwater sounds propagating from any direction. By amplifying and recording the electrical signals produced by a hydrophone, sound in the sea can be measured with great precision. Although a single hydrophone records sound arriving from any direction, several hydrophones can be simultaneously deployed in an array, and the resulting signals can then be manipulated to “listen” in any direction with even greater sensitivity than a single hydrophone element. Whether within an array or as a single element, the hydrophone is the basic sensor of underwater acoustics. Things to consider when selecting a hydrophone include receiving response, beam width, and depth rating.
Hydroplane	A fast motorboat with a hull shaped so that at speed planing forces support the boat′s weight, rather than simple buoyancy. A hydroplane moving at speed thus relies on the water for lift instead of buoyancy. Also hydro or thunderboat.
IACS	The International Association of Classification Societies.
Ice class	A notation assigned by a ship classification society or a national government authority to denote a ship's level of strengthening and other arrangements enabling her to navigate through sea ice. In some cases, an ice class also establishes the performance requirements for a vessel operating in sea ice.
Icebreaker	A special-purpose ship or boat designed to move and navigate through ice-covered waters.
Idlers	Members of a ship's company not required to serve watches. In general, these were specialist tradesmen such as the carpenter and the sailmaker.
In ballast	Also in ballast condition (of a vessel) having only ballast and no cargo as a load.
In irons	When a sailing vessel has lost its forward momentum while heading into the wind, rendering it unable to steer. Also in stays.
In ordinary	An 18th- and 19th-century term originally used to refer to a naval vessel that is out of service for repair or maintenance, later coming to mean naval ships in reserve with no more than a caretaker crew.
In way of	In the vicinity of; in the area of.
In-water survey	A method of surveying the underwater parts of a ship while it is still afloat instead of having to drydock it for examination of these areas as was conventionally done.
Inboard	1. Situated within a vessel. 2. Situated within a vessel and positioned close (or closer relative to another object) to her centerline.
Inboard motor	An engine mounted within the hull of a vessel, usually driving a fixed propeller by a shaft protruding through the stern. Generally used on larger vessels. See also sterndrive and outboard motor.
Inboard-outboard drive system	See sterndrive.
Inertial Navigation Systems	When you spin a gyroscope, its axle wants to keep pointing in the same direction. If you mount the gyroscope in a set of gimbals so that it can continue pointing in the same direction, it will. This is the basis of the gyrocompass . If you mount two gyroscopes with their axles at right angles to one another on a platform, and place the platform inside a set of gimbals, the platform will remain completely rigid as the gimbals rotate in any way they please. This is this basis of inertial navigation systems (INS). In an INS, sensors on the gimbals’ axles detect when the platform rotates. The INS uses those signals to understand the vehicle’s rotations relative to the platform. If you add to the platform a set of three sensitive accelerometers, you can tell exactly where the vehicle is heading and how its motion is changing in all three directions. With this information, a ship’s autopilot or an AUV’s guidance system can keep the vehicle on its intended course.
Inglefield clip	A type of clip for attaching a flag to a flag halyard.
Inshore	1. Near (especially in sight of) or toward the shore. 2. (of a wind) Blowing from the sea to the land.
Interested Party	The party, other than the Society, having an interest in or responsibility for the Ship, product, plant or system subject to classification or certification (such as the owner of the Ship and his representatives, the ship builder, the engine builder or the supplier of parts to be tested) who requests the Services or on whose behalf the Services are requested.
Interloper	A term used by the British East India Company in the seventeenth century for a merchant ship operating in violation of the company's monopoly over trade between England (later the United Kingdom) and ports east of the Cape of Good Hope. If caught, an "interloper" and her cargo could be confiscated, and her crew faced harsh penalties.
Iron Mike	A slang term for autopilot.
Iron topsail	An auxiliary motor on a schooner.
Iron wind	What sailors call inboard engines.
Ironboat	Also oreboat. A Great Lakes term for a vessel primarily used in the transport of iron ore.
Ironclad	A steam-propelled warship protected by iron or steel armor plates of the period from 1859 until the 1890s (when the term "ironclad" fell out of use).
Island	The superstructure of an aircraft carrier that extends above the flight deck. A carrier that lacks one is said to be flush-decked.
Jack	1. A sailor. Also jack tar or just tar. 2. (jack flag) A national or other official flag flown on a short jackstaff at the bow of a vessel indicating nationality or subordination to a navy or other particular seagoing service or to a government department or subnational government (such as a state or province), or to indicate membership in a yacht club. Typically, crew members spoke of the jack as if it were a member of the crew. A jack contrasts with an ensign, which is a flag with a generally similar purpose flown from the vessel′s stern. Typically, vessels fly a jack while in port and an ensign while at sea (in daylight hours).
Jack dusty	A naval store clerk.
Jack tar	A sailor dressed in "square rig" with square collar. Formerly with a tarred pigtail.
Jackass-barque	A sailing ship with three or more masts, of which the foremast is square-rigged and the main is partially square-rigged (topsail, topgallant, etc.) and partially fore-and-aft-rigged (course). The mizzen mast is fore-and-aft-rigged. Also jackass bark.
Jackline	On a yacht, a deck lifeline of rope or (preferably) flat tape, running fore and aft, to which the crew can clip their harnesses for safety. Sometimes called a jackstay, though this is a misnomer as a jackline is a line rather than a stay. The line must be very strong to take the weight of all crew clipped to it.
Jackstaff	A small vertical pole on the bow of a vessel upon which is flown its flag, or jack. The jackstaff was introduced in the 18th century.
Jackstay	1. A rope, bar, or batten running along a ship's yard, to which is attached the head of a square sail. 2. A stay for racing or cruising vessels used to steady the mast against the strain of the gaff.
Jacob's ladder	Also Jacobs ladder. 1. A flexible hanging ladder consisting of vertical ropes or chains supporting horizontal rungs, used to allow access over the side of a ship, either to transfer between the ship and another vessel alongside it or to perform maintenance tasks along the side of the ship. Sometimes mistakenly referred to as a pilot ladder, which differs from a Jacob′s ladder in its use of spreaders and in terms of specific regulations governing step size and step spacing.
Jetsam	Floating debris ejected from a ship. See also flotsam.
Jetty	A man-made pier in a marina or open water, typically made of wood or rocks and rising several feet above high tide in order to create a breakwater, shelter, channel, erosion control, or other function.
Jib	A triangular headsail at the front of a sailing vessel. The tack is attached to the bow or to a bowsprit. May be the only headsail, or one of several – in which case the jib is set forward of the fore staysail. A large jib that overlaps the mainmast is called a genoa or genny.
Jib top	A high-clewed overlapping headsail for beam reaching in medium to strong winds.
Jibboom	A spar used to extend the bowsprit.
Jibe	See gybe.
Jibe-ho	See gybe-oh.
Jigger-mast	The fourth mast on a ship, or the aftmost mast where it is smallest on vessels of less than four masts.
Joggle	A slender, triangular recess cut into the faying surface of a frame or steamed timber to fit over the land of clinker planking, or cut into the faying edge of a plank or rebate to avoid feather ends on a strake of planking. The feather end is cut off to produce a nib. The joggle and nib in this case is made wide enough to allow a caulking iron to enter the seam.
Jollies	Traditional Royal Navy nickname for the Royal Marines.
Jolly boat	A type of ship's boat used to ferry crew and stores.
Jonah	A person (either a sailor or a passenger) who carries a jinx, one whose presence on board brings bad luck and endangers the ship.
Jonah's lift	The throwing overboard of a man considered to be a Jonah, almost always in the dark of night.
Junk	1. Old cordage past its useful service life as lines aboard a ship. The strands of old junk were teased apart in a process known as "picking oakum". 2. A sailing ship of classic Chinese design with characteristic full batten sails that span the masts usually on unstayed rigs.
Jury rig	Both the act of rigging a temporary mast and/or sails and the name of the resulting rig. A jury rig would be built at sea when the original rig was damaged, and then used to sail to a harbor or other safe place for permanent repairs. Also used as a general term for a temporary repair, hence "jury rudder", "jury tiller", etc.
K BO Line	A line or mark on the aft end of a ship indicating the true centerline of the transom.
Kaep	A type of proa native to Palau.
Kedge	Also kedge anchor. A type of relatively light anchor.
Kedging	A technique for moving or turning a ship by using a kedge. The kedge anchor may be dropped while in motion to create a pivot and thus perform a sharp turn. It may also be carried away from the ship in a smaller boat, dropped, and then weighed, pulling the ship forward.
Keel	The principal central longitudinal structural member of a hull, positioned at or close to the lowest point of the hull. Where the keel protrudes below the surface of the hull, it provides hydrodynamic resistance to the lateral forces that give rise to leeway. A ballast keel of (typically) lead or cast iron may be fastened underneath the structural keel in sailing vessels to provide stability and usually also additional hydrodynamic resistance effects. See also bilge keel.
Keel	This is perhaps the most critical structural member of any vessel compared to the backbone or the foundation of any building. Keel is the bottommost structural member of the ship and runs longitudinally unstinted from forward to aft. ... (more at Keel)
Keelhauling	A type of maritime punishment by which one is dragged under the keel of a ship.
Keelson	Also kelson. A baulk of timber or a steel girder immediately above the keel that forms the backbone of a wooden ship. A chine keelson of more modest proportions is fitted at the junction of the floors and frames.
Kellet	See anchor sentinel.
Kentledge	Weights, usually pig iron, used as permanent, high-density ballast.
Ketch	A two-masted fore-and-aft-rigged sailboat with the aft mast (the mizzen) mounted (stepped) afore the rudder.
Kicking strap	1. A rope, tackle, or hydraulic ram running from the mast at or just above deck level to a point partway along the boom of a yacht's mainsail or mizzen. Its function is to pull the boom down, flattening the sail in strong winds, reducing twist, and preventing the boom from kicking up when running. 2. A chain rigged from rudder to quarter that is tight at anchor, stopping the rudder from kicking and reducing pressure on its gudgeons.
Killick	1. A small anchor. 2. A seaman promoted to the first step of the promotion ladder in the British Royal Navy. A fouled anchor is the substantive badge of non-commissioned officers, signifying that the wearer is an able seaman skilled to cope with the awkward job of dealing with a fouled killick.
King plank	The centerline plank of a laid deck. Its sides are often recessed, or nibbed, to take the ends of their parallel curved deck planks.
King post	1. On an American wooden-hulled steamboat, a type of mast or stanchion located along the vessel's centerline from which heavy chains (and later cables) were suspended to support the weight of the hull and provide stiffening, in much the same manner as the cables on a suspension bridge; usually used in conjunction with a hog frame. 2. On a cargo ship, a strong vertical post from which a derrick or boom is suspended.
Kingston valve
Kissing the gunner's daughter	Bending over the barrel of a gun for punitive beating with a cane or cat o' nine tails.
Kitchen rudder	A hinged cowling around a fixed propeller, allowing the drive to be directed to the side or forwards in order to maneuver the vessel.
Kite	A spinnaker.
Knee	1. A structural element connecting two parts roughly at right angles, e.g. deck beams to frames. 2. A vertical rubber fender used on pushboats or piers, sometimes shaped like a human leg bent slightly at the knee.
Knighthead	1. A mitred backing timber that extends the after line of the rabbet in the stem to give extra support to the ends of the planks and the bowsprit. 2. A bollard or bitt.
Knock	See header.
Knockdown	The condition of a sailboat being pushed abruptly over on its side, i.e. to horizontal or "on its beam-ends", with the masts parallel to the water surface.
Knot	A unit of speed equivalent to 1 nautical mile (1.8520 km; 1.1508 mi) per hour. Originally the speed of a moving vessel was measured by paying out a line from the stern; the line was tied into a knot every 47 feet 3 inches (14.40 m), and the number of knots paid out in 30 seconds gave the speed through the water in nautical miles per hour. Sometimes "knots" is mistakenly stated as "knots per hour", but the latter is a measure of acceleration (i.e. "nautical miles per hour per hour") rather than of speed. Both vessel speed and wind speed are commonly reported in knots.
Know the ropes	A sailor who knows the ropes can identify all the many ropes used in working a sailing vessel. On a square rigged ship, there would typically be more than 130 named ropes in the running rigging which are made fast at deck level – the majority of these are duplicated on both the port and starboard sides, so doubling that count. In order to know the ropes, a sailor must first learn the ropes. There were conventions with the positioning of all the many ropes belayed at deck level on a square-rigged ship, so a newly signed-on hand would quickly know where to find a particular rope on a strange ship.
Lace	To attach a sail to a spar by passing a rope through eyelet holes and around the spar or its jackstay.
Ladder	On board a ship, all "stairs" are called ladders, except for literal staircases aboard passenger ships. Most "stairs" on a ship are extremely narrow and nearly vertical, hence the name.
Lagan	Cargo that has been thrown overboard, sunk to the seabed, and buoyed so it can be found later.
Laid up	To be placed in reserve or mothballed. The latter usage in modern times refers to a specific set of procedures used by the United States Navy to preserve ships in good condition.
Lakeboat	Great Lakes slang for a vessel that spends all of her time on any of the five Great Lakes.
Laker	Great Lakes slang for a vessel that spends all of her time on any of the five Great Lakes.
Lakeshoring
Land lubber	A person unfamiliar with being on the sea or with the workings of a seafaring vessel.
Landfall	1. Arrival at a coastline by ship. 2. In now-obsolete usage, the first land discovered after a sea voyage.
Landmark	An object ashore that is visible from sea and sufficiently distinct such that it is marked on nautical charts for the purpose of fixing position while at sea.
Landsman	A military rank for a naval recruit, used in the United Kingdom in the 18th century and the first half of the 19th century and in the United States in the 19th and early 20th centuries.
Lang's lay	Rope in which the lay of the strands is on the same hand as the lay of the constituents of the strands.
Langrage	1. Another name for canister shot. 2. Solid shot suitable for damaging rigging.
Lanyard	A light rope that suspends a small item to prevent loss or is used to operate something by pulling on it.
Larboard	An obsolete term for the left side of a ship. Derived from "lay-board", which provided access between a ship and a quay when ships normally docked with the left side to the wharf. Later replaced by "port side" or "port", to avoid confusion with starboard.
Large	See by and large.
Lateen sail	Also Latin-rig. A triangular, sometimes quadrilateral, fore-and-aft sail set on a long yard mounted at an angle to the mast.
Lateral system	A system of aids to navigation in which characteristics of buoys and beacons indicate the sides of the channel or route relative to a conventional direction of buoyage (usually upstream).
Lattice mast
Launch	1. The largest ship's boat carried by a warship – usually an open boat and, in more recent times, fitted with an engine. Historically, both were fitted to be rowed or sailed vessels. 2. In modern usage, a large motorboat; e.g. a harbor master's launch.
Lay	1. To come and go, used in giving orders to the crew, e.g. "lay forward" or "lay aloft", respectively indicating that the crew should move to the forward part of the ship or take up positions aloft. 2. To direct the course of a vessel.
Lay day	An unexpected delay time during a voyage often spent at anchor or in a harbor. It is usually caused by bad weather, equipment failure, or needed maintenance.
Lay to	See also heave to. To bring a vessel into the wind and hold her stationary. A vessel doing this is said to be laying to.
Lay-Up / Laid-Up	A condition in which the unit is taken out of service. One of the key considerations in the early planning of a lay-up is its expected duration as this will affect what measures need to be taken. There are two lay-up conditions commonly referred to in the shipping industry: Hot Lay-up – This is typically for a period between 1 and 12 months. A reduced crew, normally below safe manning levels, will remain on board to conduct necessary maintenance and keep some of the ship’s machinery in operation, as the ship will normally generate its own electrical power to energize important ship systems. Ships in hot lay-up will typically require a short time to prepare for reactivation or reinstatement, but in some cases drydocking may be required.
Laying down	Laying the keel of a ship in a shipyard, and thereby beginning her construction. The age of a ship is often indicated by giving the date it was laid down.
Laytime	The amount of time stipulated in a voyage charter for a vessel to be loaded or unloaded. If a vessel is loaded or unloaded in less than the laytime, the shipowner may be required to pay despatch to the charter party. If the loading or unloading takes longer than the laytime, the charter party may be required to pay demurrage to the shipowner.
Lazaret	Also lazarette or lazaretto. 1. A small stowage locker at the aft end of a boat.
Lazy jacks	Also lazy jacks. A network of cordage rigged to a point on the mast and to a series of points on either side of the boom that cradles and guides the sail onto the boom when the sail is lowered.
Lazy line	Also slime line. A line used for stern-to mooring attached to a floating pontoon or harbor wall which leads back to a seabed mooring.
Leach	Also leech. The after edge of a sail.
Lead	1. A plummet or mass of lead attached to a line, used in sounding depth at sea. 2. In former usage, to estimate velocity in knots.
Leadline	Also sounding line. An instrument used in navigation to measure water depth; the line attached to a lead.
Leadsman	A sailor who takes soundings with a lead, measuring the depth of the water.
League	A unit of length used to measure distances, normally equal to three nautical miles, but varies by nationality.
Learn the ropes	To be trained in the identification and proper use of the many various ropes used on a sailing ship. An apprentice sailor, especially on a square-rigged ship, needs to know which rope of the many that are belayed at deck level does which job. A small square sail will have, at a minimum, two sheets, two clewlines, several buntlines, and two braces, and may also have a halyard. A single mast may have up to five square sails. To do his job, a sailor must be able to identify each rope from all the many options – and in the dark. Slacking or hauling the wrong one may not only be inefficient but also potentially dangerous. Once proficient in these tasks, a sailor is said to "know the ropes".
Lee helm	The tendency of a sailboat to turn to leeward in a strong wind when there is no change in the rudder's position. This is the opposite of weather helm and is the result of a dynamically unbalanced condition. See also center of lateral resistance.
Lee shore	A shore downwind of a ship. A ship that cannot sail well to windward risks being blown onto a lee shore and grounded.
Lee side	Also leeward side or simply leeward. The side of a ship that is sheltered from the wind; i.e. the side that is downwind, or in the direction toward which the wind is blowing. Contrast weather side or windward.
Lee-oh	Also hard alee. A command to come about (tack through the wind) on a sailing boat. The response by the helmsman to indicate the order has been carried out, is "helm's alee"
Leeboard	A large fan-shaped wooden board or fin mounted in pairs on the side of a boat. They can be lowered on the lee side of the ship to reduce leeway (similarly to a centerboard on a dinghy).
Leeboard irons	The iron bars that run from the mainmast case to the head of each leeboard, which they support.
Leeboard pendant	A wire connecting the fan of the leeboard to a winch on the barges quarter. They control the fall of the leeboard.
Leech	Also leach. The aft or trailing edge of a fore-and-aft sail, the leeward edge of a spinnaker, or a vertical edge of a square sail. The leech is susceptible to twist, which is controlled by the boom vang, mainsheet, and, if rigged with one, the gaff vang.
Leeward	(pronounced /ˈljuːərd/ in nautical use) In the direction toward which the wind is blowing. Contrast windward.
Leeway	The amount that a ship is blown leeward by the wind. Also the amount of open free sailing space available to the lee side of a vessel before encountering hazards. See also weatherly.
Leg	In navigation, a segment of a voyage between two waypoints.
Length between perpendiculars	Also p/p, p.p., pp, LPP, LBP, or Length BPP. The length of a vessel along the waterline from the forward surface of the stem or main bow perpendicular member, to the after surface of the sternpost or main stern perpendicular member. The measure generally allows for a reasonable estimate of the vessel's carrying capacity, as it excludes the small, often unusable volume contained in her overhanging ends.
Length overall (LOA)	The maximum length of a vessel's hull measured parallel to the waterline, usually measured on the hull alone, and including overhanging ends that extend beyond the main bow and main stern perpendicular members. For sailing vessels, this may exclude the bowsprit and other fittings added to the hull, but sometimes bowsprits are included.
Let go and haul	An order indicating that the ship is now on the desired course relative to the wind and that the sails should be trimmed (hauled) to suit.
Letter of marque and reprisal	Also simply letter of marque. An official warrant granted to a privateer condoning specific acts of piracy against a specific target as a redress for grievances.
Liberty	A relatively short period when a sailor is allowed ashore for recreation. See also shore leave.
Licensed ship	A term used by the British East India Company from the 17th to the 19th centuries for merchant ships not under charter to it which it nevertheless permitted under a license issued by the company to trade between England (later the United Kingdom) and ports east of the Cape of Good Hope, a trade over which the company otherwise held a strict monopoly. The company placed strict controls on what ports a licensed ship could visit and what kinds of trade it could engage in. A licensed ship that violated these rules became an interloper and faced harsh penalties if caught.
Lie to	To arrange a ship's sails so that they counteract each other. A ship in this condition or in the process of achieving this condition is said to be lying to.
Lifebelt	Also lifebuoy, lifejacket, life preserver, and personal flotation device (PFD). A portable or wearable device such as a buoyant ring or inflatable jacket designed to keep a person afloat in the water.
Lifeboat	1. (shipboard lifeboat) A small boat kept on board a vessel and used to take crew and passengers to safety in the event of the ship being abandoned. 2. (rescue lifeboat) A small boat usually launched from shore and used to rescue people from the water or from vessels in difficulty.
Liferaft	An inflatable, sometimes covered raft used in the event of a vessel being abandoned or in the evacuation of an aircraft after a water landing.
Lift	1. A rope that supports a spar on a sailing vessel. Examples include the topping lift on the boom of a fore and aft rigged sail, or the lifts on the yard of a square rigged sail, which can adjust the yard to the horizontal or cock-bill the yard to get it out of the way when unloading cargo or alongside another vessel. 2. An enabling shift in the direction of the wind that allows a close-hauled sailing ship to point up from its current course to a more favorable one. This is the opposite of a header.
Light irons	Iron bars mounted near the main shrouds that support the navigation lights.
Light screens	Boards on which the navigation lights are hooked and which shield the direction that the red or green light shows.
Lighter	A flat-bottomed barge used to transfer goods and passengers to and from moored ships, traditionally unpowered and moved and steered using "sweeps" (long oars), with their motive power provided by water currents.
Lightering	The process of transferring cargo from one vessel to another in order to reduce the draft of the first vessel, typically done to allow a vessel to enter a port with limited depth or to help free a grounded vessel.
Lighting	is used underwater to provide illumination for divers, for submersible pilots and passengers, and for cameras . Three general classes of lights exist: incandescent, arc, and LEDs. Incandescent lights work by heating a filament to the point where it radiates light. Quartz halogen lights are the most commonly used incandescent. The name derives from the quartz glass bulb used that is filled with a halogen gas which is used to redeposit evaporated filament materials back on the filament. Incandescent lights are inexpensive but bulbs are fragile and have relatively short life times. ... (more at Lighting)
Lightvessel	Also lightship. A permanently anchored vessel performing the functions of a lighthouse, typically in a location where construction of the latter is impractical. These have largely been replaced by buoys or, as construction techniques have improved, actual lighthouses.
Limber board	A part of the ceiling alongside the keelson, easily removable for cleaning out the limber holes.
Limber hole	A channel cut in the underside of a frame, close to the keel, to allow bilge water to drain away to the pump well, rather than being trapped between each set of frames.
Line	The correct nautical term for the majority of the cordage or "ropes" used on a vessel. An individual line will always have a more specific name (e.g. the mizzen topsail halyard) that specifies its use.
Line astern	In naval warfare, a line of battle formed behind a flagship.
Liner	1. During the Age of Sail, a ship-of-the-line, or a major warship capable of taking its place in the main battle line of fighting ships. 2. Any cargo or passenger ship running scheduled service along a specific route with published ports of call, excluding ferries and other vessels engaged in short-sea trading. When referring to cargo ships, "liner" contrasts with "tramp", which refers to a ship engaged in spot-market trade that does not follow a regular schedule or make regular calls at specific ports. When referring to passenger ships, "ocean liner" refers to ships providing scheduled transportation between regular ports of call, but excludes cruise ships, which voyage for recreational purposes and not primarily as a form of transportation between ports.
List	The degree or angle to which a vessel leans or tilts to one side, on the roll axis, at equilibrium, i.e. with no external forces acting upon it. The term typically refers to a lean caused by flooding or improperly loaded or shifted cargo, as opposed to heeling, which is a consequence of external forces. A vessel with such a lean is said to be listing. Compare loll.
Lizard	A short length of rope with an eye, used to hold another rope in position.
Loaded to the gunwales	Literally, having cargo loaded as high as the ship's rail. The term is also used as an idiom meaning "extremely drunk".
Lofting	In boat construction, a drafting technique used to convert a scaled drawing to full size.
Loggerhead	1. A bollard mounted in the sternsheets of a whaleboat for snubbing the whale line as a harpooned whale swam away from the boat. 2. An iron ball attached to a long handle, used for driving caulking into seams and (occasionally) in a fight; hence the expression "at loggerheads".
Loll
Long Forties	An area of the northern North Sea which is fairly consistently 40 fathoms (240 feet; 73 metres) deep. On nautical charts with depths indicated in fathoms, it appears as a long area with many "40" notations.
Long stay	The relative slackness of an anchor chain; this term means taut and extended.
Longboat	1. In the Age of Sail, a double-banked open boat carried by a sailing ship, rowed by eight or ten oarsmen, two per thwart, although designed also to be rigged for sailing; more seaworthy than a cutter or dinghy and with a beam greater than that of a gig. Eventually supplanted by the whaleboat. 2. The largest, and thus the most capable, of boats carried on a ship.
Longitudinals	Longitudinals are stiffeners that run in a longitudinal direction, i.e., from forward to aft. They resist the longitudinal loads and their effects like bending stresses and buckling and support other connected members. They have definite scantlings and are uniformly spaced depending on the vessel’s bottom and the decks.
Longliner	A fishing vessel rigged for longline fishing ("longlining").
Longship	A type of ship invented and used by the Vikings for trade, commerce, exploration, and warfare, evolving over several centuries and appearing in its complete form between the 9th and 13th centuries.
Lookout
Loose cannon	An irresponsible and reckless individual whose behavior (either intentionally or unintentionally) endangers the group he or she belongs to. The term refers to a hypothetical literal loose cannon which, weighing thousands of pounds, would crush anything and anyone in its path, and possibly even break a hole in the hull, thus endangering the seaworthiness of the whole ship.
Loose-footed	A fore-and-aftmainsail that is not connected to a boom along its foot.
Lorcha	A sailing vessel of 30 to 150 tons burthen developed around 1550 that has a junk rig with Cantonese or other Chinese-style batten sails on a Portuguese or other European-style hull. The design combines the ease of handling of a junk rig with the greater speed, cargo capacity, and ease of repair of the European-style hull.
Lower deck	1. The deck of a ship immediately above the hold. 2. In British usage, those members of a ship's company who are not officers, often used in the plural (e.g. "the lower decks").
Lowers	The lower brails on the mainsail.
Lubber's hole	A port cut into the bottom of a masthead or top (crow's-nest) allowing easy entry and exit. It was considered "un-seamanlike" to use this method rather than going over the side from the shrouds, and few sailors would risk the scorn of their shipmates by doing so (at least if there were witnesses). In practice, it is often actually quicker and easier for a fit sailor to climb outside the masthead than through the lubber's hole.
Lubber's line	A line or mark inside or on a compass case or binnacle indicating the direction of the ship's head.
Lucky bag	1. A locker or compartment for storage of unclaimed articles. 2. U.S. Naval Academy yearbook.
Luff	1. The forward edge of a sail. 2. The fullest or roundest part of a ship's bow.
Luff and touch her	To bring a vessel so close to the wind that the sails shake.
Luff barge	Also paddy boat. An 18th-century term for a sailing barge with a rounded bow and not a swim-head.
Luff perpendicular (LP)	The shortest distance between the clew and the luff, which is a perpendicular line from the luff to the clew. Commonly given as a percentage of the "J" measurement.
Luff up	To steer a sailing vessel more towards the direction of the wind until the pressure is eased on the sheet.
Luffing	1. (of a sailing vessel) Being steered far enough to windward that the sail is no longer completely filled with wind; in such a state, the luff of a fore-and-aft sail begins to flap first. 2. Loosening a sheet so far past optimal trim that the sail no longer completely fills with wind.
Lug sail	A four-sided fore-and-aft sail supported by a spar along the top that is fixed to the mast at a point some distance from the center of the spar. A dipping lug had to be moved to the other side of the mast when tacking (in larger vessels, by partially lowering the sail and hauling down either the peak or the throat to move the yard across). A standing lug can be used on either tack in the same position. It was common for British fishing luggers to have a dipping lug on the foremast and a standing lug on the mizzen.
Lugger	A sailing vessel with lug sails set on one, two, or more masts and perhaps lug topsails, widely used as traditional fishing boats, particularly off the coasts of France, England, and Scotland; also used as privateers and smugglers.
Lumber hooker	A Great Lakes ship designed to simultaneously carry her own deck load of lumber and to tow one or two barges. The barges were big old schooners stripped of their masts and running gear to carry large cargoes of lumber.
Lying ahull	Waiting out a storm by dousing all sails and simply letting the boat drift.
Lying to	See lie to.
M.V. (or MV)	An abbreviation for Motor Vessel, used before a ship's name.
M.Y. (or MY)	An abbreviation for Motor Yacht, used before a yacht's name.
Mack	A structure which combines the radar mast and the exhaust stack of a surface ship, thereby saving valuable deck space.
Mae West
Magazine	Also ship′s magazine. The ammunition storage area aboard a warship.
Magnetic bearing	An absolute bearing using magnetic north.
Magnetic north	The direction towards the North Magnetic Pole. Varies slowly over time.
Magnetometers	are used to measure anomalies in the earth’s magnetic field. These can be due to local geologic features or manmade objects in the area (i.e., ship wrecks). Underwater magnetometers are typically towed behind a ship. Proton magnetometers operate on the principal that the protons in all atoms are spinning on an axis aligned with the magnetic field. Ordinarily, protons tend to line up with the earth’s magnetic field. When subjected to an artificially-induced magnetic field, the protons will align themselves with the new field. When this new field is interrupted, the protons return to their original alignment with the earth’s magnetic field. As they change their alignment, the spinning protons precess, or wobble, much as a spinning top does as it slows down. The frequency at which the protons precess is directly proportional to the strength of the earth’s magnetic field. ... (more at Magnetometers)
Maiden voyage	The first voyage of a ship in its intended role, i.e. excluding trial trips.
Maierform bow	A V-shaped bow introduced in the late 1920s which allowed a ship to maintain a given speed with less power, improved seakeeping, increased reserve buoyancy, reduced pitching movements, and improved propeller immersion to increase performance in rough seas.
Main	The high sea; the open ocean.
Main deck	The uppermost continuous deck extending from bow to stern.
Mainbrace	Either of the braces attached to the yard of the mainsail (the largest and lowest sail on the mainmast) on a square-rigged vessel.
Mainmast	Also main. 1. The tallest mast on a ship with more than one mast, especially the tallest mast on a full-rigged ship.
Mainmast head	The top of a sailing vessel's mainmast.
Mainmastman	A sailor assigned to the mainmast.
Mains	The main brails on the mainsail.
Mainsheet	A sail control line that allows the most obvious effect on mainsail trim. Primarily used to control the angle of the boom, and thereby the mainsail, this control can also increase or decrease downward tension on the boom while sailing upwind, significantly affecting sail shape. For more control over downward tension on the boom, a boom vang may be used.
Mainstay	The stay running from the top of the mainmast to the bottom of the foremast, or from the top of the foremast to the ship's stem.
Making way	When a vessel is moving under its own power.
Man overboard	1. An emergency call that alerts the crew that someone aboard has gone overboard and must be rescued. 2. A person who has fallen into the water from a ship or boat – the object of the resulting rescue attempt.
Man the rails	To station the crew of a naval vessel along the rails and superstructure of the vessel as a method of saluting or rendering honors.
Man the yards	To have all of the crew of a sailing vessel not required on deck to handle the ship go aloft and spread out along the yards. Originally used in harbors to display the whole crew to harbor authorities and other ships present to show that the vessel's guns were not manned and hence her intentions were peaceful, manning the yards has since become a display used in harbor during celebrations and other special events.
Man-of-war	Also man o' war. A warship from the Age of Sail.
Manifest	A document listing the cargo, passengers, and crew of a ship for the use of customs and other officials.
Marconi rig	An archaic term for Bermuda rig. The mainsail is triangular, rigged fore-and-aft with its luff fixed to the mast. The foresail (jib) is a staysail hanked onto the forestay. Refers to the similarity of the tall mast to a radio aerial.
Marina	A docking facility for small ships and yachts.
Marine	2. An alternative term for a navy, uncommon in English but common in other languages.
Marine sandglass (or glass)	An hourglass-like timekeeping instrument used aboard ships from at least the 14th century until reliable mechanical timepieces replaced it in the early 19th century. Marine sandglasses measured the passage of time in 30-minute increments to regulate time on watch, to measure a boat's speed, and to assist in determining a ship's position by measuring the time elapsed while she was on a given course.
Mariner	A sailor.
Maritime	1. Of or related to the sea (e.g., maritime activities, maritime law, maritime strategy). 2. Bordering on the sea (e.g., maritime provinces, maritime states).
Marlinspike	A tool used in ropework for tasks such as unlaying rope for splicing, untying knots, or forming a makeshift handle.
Mast	A vertical pole on a ship that supports sails or rigging. If a wooden multi-part mast, this term applies specifically to the lowest portion.
Mast case	A yachtsman's tabernacle. The iron fitting in which the heel of the mast is mounted.
Mast step	The place in the hull where the lowest point of a mast rests, taking the weight of the mast and the thrust imposed by the tension of the rigging, and preventing lateral and fore and aft movement of the bottom of the mast. With a wooden hull and mast, this is usually achieved by having a socket cut in the top of the keelson, a floor or some other major structural component. A tenon cut into the bottom of the mast sits snugly in the socket. With a deck-stepped aluminum mast, the step may consist of a metal fitting bolted to the deck, to which bolts a matching fitting at the bottom of the mast.
Mast stepping	The process of raising a mast.
Master
Masthead	A small platform partway up the mast, just above the height of the mast's main yard. A lookout is stationed here, and men who are working on the main yard will embark from here. See also crow's nest.
Masthead light	A white running light displayed at the front of a vessel.
Material	Military equipages of all descriptions for the naval services. The bombs, blankets, beans, and bulletins of the Navy and Marine Corps. Taken from Nelson's British navy as the US services became professional. See also materiel – military supplies, equipment and weapons.
Mediterranean mooring	Also Med moor and Tahitian mooring. A method of mooring stern-to.
Megger test	A method of testing making use of an insulation tester resistance meter that will help to verify the condition of electrical insulation. Insulation resistance quality of an electrical system degrades with time, environment condition i.e. temperature, humidity, moisture and dust particles.
Merchant marine	A collective term for all merchant ships registered in a given country and the civilians (especially those of that nationality) who man them; the ships and personnel in combination are said to constitute that country's merchant marine. Called the merchant navy in the United Kingdom and some other countries.
Merchant mariner	A civilian officer or sailor who serves in the merchant marine. Sometimes such personnel are incorrectly called "merchant marines", but both merchant mariners and marines frown on this term; although merchant mariners are part of the merchant marine, they are civilians and are not in any way marines, which are a specialized type of military personnel.
Merchant navy	A name bestowed upon the merchant marine of the United Kingdom by King George V, and since adopted by some other countries as well. The merchant navy's personnel are civilians, and the term "merchant navy" does not imply that they or their ships are a part of the navy. Synonymous with the term merchant marine.
Merchantman	A merchant ship - any non-naval passenger- or cargo-carrying vessel, including cargo ships, tankers, and passenger ships but excluding troopships.
Mess	Also messdeck. 1. An eating place aboard a ship.
Mess deck catering	A system of catering in which a standard ration is issued to a mess supplemented by a money allowance, which the mess may use to buy additional victuals from the pusser's stores or elsewhere. Each mess was autonomous and self-regulating. Seaman cooks, often members of the mess, prepared the meals and took them, in a tin canteen, to the galley to be cooked by the ship's cooks. As distinct from "cafeteria messing" where food is issued to an individual hand, which is now the general practice.
Metacenter	The midway point between a vessel's center of buoyancy when upright and her center of buoyancy when tilted.
Metacentric height (GM)	A measurement of the initial static stability of a vessel afloat, calculated as the distance between her center of gravity and her metacenter. A vessel with a large metacentric height rolls more quickly and therefore more uncomfortably for people on board; a vessel with a small metacentric height will roll sluggishly and may face a greater danger of capsizing.
Middle Passage
Middles	The middle brails on the mainsail, higher than the lowers, and lower than the mains.
Midship house	A superstructure built over the midships section of the hull, often housing the bridge and officers quarters, as well as passenger quarters aboard cargo liners. A common feature of tankers, cargo liners, and cargo ships up until the mid-20th century, when ship design moved away from the use of midship houses.
Midshipman	1. During the 17th century, a naval rating for an experienced seaman. 2. From the 18th century, a naval commissioned officer candidate.
Midshipman's hitch	An alternative to the Blackwall hitch, preferred if the rope is greasy. Made by first forming a Blackwall hitch and then taking the underneath part and placing it over the bill of the hook.
Midshipman's nuts	Broken pieces of biscuit as dessert.
Midshipman's roll	A slovenly method of rolling up a hammock transversely and lashing it endways by one clue.
Midships	Also midship. A shortened form of amidships, with both alternative meanings.
Mile	See nautical mile.
Millers	Shipboard rats
Misstay	To be "in irons" (i.e. to lose forward momentum) when changing tack.
Mizzen	1. A mizzen sail is a small sail (triangular or gaff) on a ketch or yawl set abaft the mizzenmast. 2. A mizzen staysail is an occasional lightweight staysail on a ketch or yawl, set forward of the mizzenmast while reaching in light to moderate airs.
Mizzenmast	Also mizzen. The third mast, or the mast aft of the mainmast, on a ship.
Mobile crane vessel or crane ship	A ship with a crane and specialized for lifting heavy loads.
Mold	A template of the shape of the hull in transverse section. Several molds are used to form a temporary framework around which a hull is built.
Mold loft	Where the lines of the ship are drawn out full-size and the templates for the timbers are made.
Mole	A massive structure, usually of stone or concrete, used as a pier, breakwater, or causeway between places separated by water. May have a wooden structure built upon it and resemble a wooden pier or wharf, but a mole differs from a pier, quay, or wharf in that water cannot flow freely underneath it.
Monitor	1. A turreted ironclad warship of the second half of the 19th century characterized by low freeboard, shallow draft, poor seaworthiness, and heavy guns, intended for riverine and coastal operations. 2. In occasional 19th-century usage, any turreted warship.
Monkey bridge	A high platform above the wheelhouse offering better visibility to the operator while maneuvering.
Monkey's fist	A ball woven out of line used to provide heft to heave the line to another location. The monkey fist and other heaving-line knots were sometimes weighted with lead (easily available in the form of foil used e.g. to seal tea chests from dampness) although Clifford W. Ashley notes that there was a "definite sporting limit" to the weight thus added.
Moor	1. To attach a boat to a mooring buoy or post. 2. To dock a ship.
Mooring	Also moorings. A place to moor a vessel.
Mother ship	Also mothership and mother-ship. A vessel that leads, serves, or carries smaller vessels, in the latter case either releasing them and then proceeding independently or also recovering them after they have completed a mission or operation. A mother ship sometimes contrasts with a tender, which often (but not necessarily) is a vessel that supports or cares for larger vessels.
Mousing	Several turns of light line around the mouth of a hook, to prevent unhooking accidents.
Mulie	A barge rigged with a spritsail main, and a large gaff rigged mizzen afore the steering wheel. It is sheeted to the saddle chock.
Multipurpose vessel	A cargo ship that has fittings to carry standard shipping containers and retractable tween decks that can be moved out of the way so that the ship can carry bulk cargo.
Multiservice tactical brevity code	Codes used by various military forces to convey complex information in a few words.
Muster drill	An exercise conducted by the crew of a ship prior to embarking on a voyage. Passengers are required to participate in the drill so that they can be instructed how to evacuate safely in the event of an emergency on board the ship.
Muster station	A specific location on a vessel planned as a gathering place during an emergency or a muster drill. If a person is believed missing, all passengers must report to their muster station for a head count.
Muzzle	Iron ban around the mast to hold the heel of the sprit.
NDE (tests)
NDT (tests)
Name ship	A ship whose name also is used to refer to her entire class of ships. Usually but not always the first ship of her class to be completed and enter service, in which case the term name ship can be used as a synonym for lead ship.
Narrowboat	A type of boat designed specifically to fit the narrow canal locks of the United Kingdom.
Narrows	A narrow part of a navigable waterway.
Natural harbor	A body of water protected from the weather by virtue of its being mostly surrounded by land, and deep enough to provide anchorage for the vessels using it.
Nautical	Of or pertaining to sailors, seamanship, or navigation; maritime.
Nautical chart
Nautical mile	A unit of length corresponding to approximately one minute of arc of latitude along any meridian arc. By international agreement, it is equivalent to exactly 1,852 meters (6,076 ft; 1.151 mi).
Naval architecture	In the engineering of seagoing vessels, naval architecture is concerned with the overall design of the ship and its propulsion through the water, while marine engineering ensures that the ship systems function as per the design. Although they have distinctive disciplines, naval architects and marine engineers often work side-by-side.
Navigation
Navigation light	Also position light or running light. A source of illumination on a vessel intended to give information to other vessels on her position, heading, or status.
Navigation rules	Rules of the road that provide guidance on how to avoid collision and also used to assign blame when a collision does occur.
Nay	A reply in the negative, synonymous with "no". The opposite of "aye".
Net cutter	1. (Fisheries patrol), also trawl wire cutter: A device employed by the Icelandic Coast Guard during the "Cod Wars" to cut the trawling wires of foreign fishing trawlers working within Iceland's claimed exclusive fisheries zones. 2. (Submarine): A device, sometimes powered by explosives, mounted on the bow of a submarine to cut through anti-submarine netting.
New Company ship	A term used for a ship trading between England and ports east of the Cape of Good Hope for the English Company Trading to the East Indies, a new company chartered in 1697 to compete with the "old" East India Company. The term fell into disuse when the two companies merged in 1707.
Night boat	(United States) A type of steamboat that provided sleeping quarters for passengers on overnight voyages, as opposed to a day boat that had no need of such facilities.
Nipper	A short rope is used to bind a cable to the "messenger" (a moving line propelled by the capstan) so that the cable is dragged along, too (used where the cable is too large to be wrapped around the capstan itself). During the raising of an anchor, the nippers were attached and detached from the (endless) messenger by the ship's boys. Hence the term for small boys: "nippers".
No room to swing  a cat	The entire ship's company was expected to witness floggings, assembled on deck. If it was very crowded, the bosun might not have room to swing the cat o' nine tails (the whip).
Nock	The throat of the mainsail.
Non-self-sustaining	See self-sustaining.
Nun	A type of navigational buoy, often cone-shaped, but if not, always triangular in silhouette, colored green in IALA region A or red in IALA region B (the Americas, Japan, Korea, and the Philippines). In channel marking its use is opposite that of a "can buoy".
Oakum	Any material, often tarred hemp fibers picked from old untwisted ropes, used for caulking gaps or seams between the planks of hulls.
Oar	A pole, usually of wood, with a blade at one end and a handle at the other, which is pivoted on a fulcrum on the side of a boat to provide propulsion by moving the blade through the water.
Oar crutch	A metal (or sometimes plastic) fitting that acts as the fulcrum point of an oar. Usually takes the form of a U-shape, with a pin underneath the bottom of the "U". The pin rotates in a socket in the gunwale of the boat; the oar rests in the "U". Often referred to as a rowlock
Ocean engineering
Ocean liner	See liner.
Oceanography
Officer’s country	The part of a naval vessel containing the residential quarters and wardroom for commissioned officers. Officer′s country is off-limits to enlisted personnel unless they are there on official business.
Offing	The more distant part of the sea as seen from the shore and generally beyond anchoring ground.
Offshore	1. Moving away from the shore. 2. (of a wind) Blowing from the land to the sea.
Offshore Systems	A number of systems designed fully or in part by marine engineers are used offshore - far away from coastlines. ... (more at Offshore Systems)
Oiler	1. (ship) A naval auxiliary ship with fuel tanks, which refuels other ships. 2. (occupation) The job title of a seaman holding a junior position in a ship's engineering crew, senior only to the engine room wiper.
Oilskins	Also oilies. Foul-weather clothing worn by sailors.
Old man	Crew's slang for the captain, master, or commanding officer of a vessel.
Old salt	Slang for an experienced mariner.
On board	Also onboard. See aboard.
On her own bottom	Plural on their own bottoms. Said of a vessel making a voyage without being carried aboard another vessel, e.g., "The yacht crossed the ocean on her own bottom," or in the plural, "Yachts rarely cross the ocean on their own bottoms."
On station	A ship's destination, typically an area to be patrolled or guarded.
On the beach	1. A Royal Navy term that means "retired from the Service." 2. On shore leave.
On the hard	A boat that has been hauled and is now sitting on dry land.
Open registry	An organization that will register merchant ships owned by foreign entities, generally to provide a flag of convenience.
Optical Oceanographic Sensors	measure the optical properties of water such as absorption, attenuation, scattering, fluorescence and volume scattering function. The instruments used to measure these parameters include: Transmissometers are devices for measuring transmission or beam attenuation. They work by shining a narrow, collimated beam of light through the water. A receiver with a narrow field of view measures how much light arrives at the other end of a set distance. Light that is lost to absorption or is scattered will not be detected. ... (more at Optical Oceanographic Sensors)
Ordinary	See in ordinary.
Ordinary seaman	1. A seaman in the British Royal Navy in the 18th century who had between one and two years of experience at sea. Later, a formal rank in the Royal Navy for the lowest grade of seaman, now obsolete. 2. The second-lowest rank in the United States Navy from 1797 to 1917, between landsman and seaman. Renamed "seaman second class" in 1917.
Ore carrier	A type of bulk carrier specially designed to carry ore.
Oreboat	Also ironboat A Great Lakes term for a vessel primarily used in the transport of iron ore.
Orlop deck	1. The lowest deck of a ship-of-the-line. 2. The deck covering in the hold.
Oscar	1. International signal for a man overboard. 2. Nickname for a water rescue training dummy. Also see paradummy.
Outboard	1. Situated outside the hull of a vessel. 2. Situated within a vessel but positioned away (or farther away, when contrasted with another item) from her centerline.
Outboard motor	A motor mounted externally on the transom of a small boat. The boat may be steered by twisting the whole motor, instead of or in addition to using a rudder.
Outdrive	The lower part of a sterndrive.
Outhaul	A line used to control the shape of a sail.
Outrigger	1. Generally, a structure projecting from the side of a vessel. 2. Any contraposing float rigging beyond the side of a vessel to improve the vessel's stability.
Outward bound	To leave the safety of port, heading for the open ocean. Over-canvassed. To have too great a sail area up to safely maneuver in the current wind conditions.
Over the barrel	Adult sailors were flogged on the back or shoulders while tied to a grating, but boys were beaten instead on the posterior (often bared), with a cane or cat o' nine tails, while bending, often tied down, over the barrel of a gun, known as kissing the gunner's daughter.
Overbear	To sail downwind directly at another ship, stealing the wind from its sails.
Overboard	Off or outside a vessel. If something or someone falls, jumps, or is thrown off of a vessel into the water, the object or person is said to have gone overboard. See "Man overboard!"
Overfalls	Dangerously steep and breaking seas due to opposing currents and wind in a shallow area, or strong currents over a shallow rocky bottom.
Overhaul	Hauling the buntline ropes over the sails to prevent them from chafing.
Overhead	The ceiling of any enclosed space below decks in a vessel, essentially the bottom of the deck above.
Overreaching	Holding a course too long while tacking.
Overtaking sea	Seas approaching a vessel from between 15° to port or starboard of astern at a speed greater than that of the vessel.
Overwhelmed	Capsized or foundered.
Owner	The registered owner, the vessel owner, the manager or any other party with the responsibility, legally or contractually, to keep the vessel seaworthy or in service, having particular regard to the provisions relating to the maintenance of class laid down in Part A, Chapter 2 of the Rules for the Classification of Ships or in the corresponding rules indicated in the specific Rules.
Ox-eye	A cloud or other weather phenomenon that may be indicative of an upcoming storm.
PIM	Points (or plan) of intended movement. The charted course for a naval unit's movements.
Packet	Also packet boat or packet ship. 1. Originally, a vessel employed to carry post office mail packets to and from British embassies, colonies, and outposts.
Packet trade	Any regularly scheduled cargo, passenger, or mail trade conducted by ship.
Packetman	A seaman aboard a ship engaged in packet trade.
Paddle box	A covering, usually made of wood, for the upper part of a paddle wheel on a paddle steamer.
Paddle guards	See guards.
Paddy wester	Traditional Royal Navy term for a young or inexperienced seaman.
Pagoda mast	A large and distinctive type of foremast installed aboard Imperial Japanese Navy battleships and battlecruisers during modernization and reconstruction of the ships in the 1930s. A pagoda mast was created by strengthening a ship's existing tripod foremast and adding platforms to it for searchlights, lookouts, shelters, and other structures, giving the mast the appearance of a pagoda temple.
Painter	A rope attached to the bow of a vessel, used to make the vessel fast to a dock or a larger vessel, including when towed astern.
Palm	A protective device, usually leather, worn on the hand when working with a sail needle to repair sails.
Pan and Tilts	are positioning devices used to remotely move cameras , lights , sonars and other devices. Pan refers to movement along the horizontal axis and tilt refers to movement in the vertical axis. A scanner is a one-axis positioner.
Panting	The pulsation in and out of the bow and stern plating as the ship alternately rises and plunges deep into the water.
Paravane	1. (weapon) A device stabilized by vanes that functions as an underwater glider and is usually streamed from the bow of a vessel and towed alongside, intended to cut the mooring of submerged mines or otherwise destroy them. 2. (water kite) A towed underwater object with hydrofoils, of use in commercial and sport fishing, water sports, marine exploration, and military operations, sometimes equipped with sensors and also of use in exerting a sideward holding force on a vessel. Also called a water kite.
Parbuckle	A method of lifting a roughly cylindrical object such as a spar. One end of a rope is made fast above the object, a loop of rope is lowered and passed around the object, which can be raised by hauling on the free end of rope.
Parley	A discussion or conference, especially between enemies, over terms of a truce or other matters.
Parrel	A movable loop or collar, used to fasten a yard or gaff to its respective mast. A parrel still allows the spar to be raised or lowered and swivel around the mast. It is sometimes made of wire or rope and fitted with beads to reduce friction.
Part brass rags	Fall out with a friend. From the days when cleaning materials were shared between sailors.
Passageway	An interior corridor or hallway on a ship.
Passenger-cargo ship	See cargo liner.
Passenger-cargoman	See cargo liner.
Patache	Also pataje or patax. A type of very light and shallow Spanish sailing vessel of the 15th through 18th centuries with two masts, resembling a cross between a brig and a schooner. Originally a type of warship, but later in use as a trading vessel.
Pawls	Small bars used to stop the barrel of a winch or capstan moving backward under an increased load or if the turning power was reduced. In early capstans, the pawls had to be manually moved in and out of the notches in which they worked. Later capstans had automatic pawls that dropped into notches as the barrel turned. In breaking out an anchor, a crew would "heave and pawl" if the bow was rising and falling with the waves, so giving a varying load on the cable.
Pay off	1. To let a vessel's head fall off from the wind (to leeward). 2. During the Age of Sail, the practice of paying a crew its wages for the voyage when a vessel completed her voyage, at which point the crew was said to be paid off.
Paying	Filling a seam (with caulking or pitch), lubricating the running rigging; paying with slush, protecting from the weather by covering with slush. See also the devil to pay.
Paymaster	The officer responsible for all money matters in Royal Navy ships including the paying and provisioning of the crew, all stores, tools, and spare parts. See also purser.
Pea coat	Heavy topcoat originally made from pilot cloth.[16] Officers and chief petty officers wear a variation with gold buttons called a reefer or a longer model called a bridge coat.
Peak	1. The upper aftermost corner of a fore-and-aft sail; used in many combinations, such as peak-halyards, peak-brails, etc. 2. The narrow part of a vessel's bow, or the hold within it.
Peaks	The uppermost brails on the mainsail. Upper and lower peaks are normal, but a barge may carry a third set, too.
Pelagic	1. Living in the open ocean rather than coastal or inland waters (e.g. a pelagic shark). 2. Taking place in the open ocean (e.g. pelagic fishing, pelagic sealing).
Pelican hook	Also called a slip-hook or Davey hook. A hook with a hinge in the curve of the hook, normally held closed by a metal ring that keeps the two hinged parts together. Can be instantly released by knocking the ring along the hook so that it frees one of the hinged parts which swings open and releases whatever the hook is holding. Often seen on opening sections of guard rails and life-raft lashings, but also used on more heavily loaded components.
Pendant	1. A length of wire or rope secured at one end to a mast or spar and having a block or other fitting at the lower end. 2. A length of wire or rope hooked to a tackle on leeboards.
Pennant	A long, thin triangular flag flown from the masthead of a military ship (as opposed to a burgee, the flags thus flown on yachts).
Petroleum Engineering	A knowledge of marine engineering proves useful in the field of petroleum engineering , as hydrodynamics and seabed integration serve as key elements in the design and maintenance of offshore oil platforms . ... (more at Petroleum Engineering)
Physical Oceanographic Sensors	are used to measure the basic physical properties of seawater. The most common are conductivity, temperature, and pressure (depth). Together these three sensors form a CTD , a common oceanographic instrument (described under its own listing in this glossary). Conductivity is the measurement of the water’s ability to conduct electric current. It is often used as a proxy for measuring salinity. The basic unit of conductance is Siemens (represented by an S), formally called the mho (omh spelled backwards). The principle by which instruments measure conductivity is simple. After an electrode consisting of two conductive plates is placed in the water, a sinewave voltage is applied across the plates and the current is measured. Electrodes are prone to corrosion , and the pumps that supply them with water can foul. ... (more at Physical Oceanographic Sensors)
Picaroon	An obsolete (circa 17th century) term for a pirate.
Picket boat	A boat on sentry duty, or one placed on a line forward of a position to warn against an enemy advance.
Pier	A raised structure, typically supported by widely spread piles or pillars, used industrially for loading and unloading commercial ships, recreationally for walking and housing attractions at a seaside resort, or as a structure for use by boatless fishermen. The lighter structure of a pier contrasts with the more solid foundations of a quay or the closely spaced piles of a wharf. In North America, the term "pier" used alone connotes either a pier used (or formerly used) by commercial shipping or one used for fishing, while in Europe the term used alone connotes a recreational pier at a seaside resort.
Pier-head jump	When a sailor is drafted to a warship at the last minute, just before she sails.
Pillars and Stanchions	Pillars and stanchions are vertical support members that act as joiners between two successive decks to transfer loads from the upper to the lower deck and subsequently to the bottom structures.
Pilot	A specially knowledgeable person qualified to navigate a vessel through difficult waters, e.g. harbor pilot, etc.
Pilot boat	A type of boat used to transport maritime pilots between land and the inbound or outbound ships that they are piloting.
Pilot ladder	A highly specialized form of rope ladder, typically used to embark and disembark pilots over the side of a ship. Sometimes confused with Jacob's ladders, but the design and construction of pilot ladders is governed tightly by international regulation and includes spreaders – elongated versions of the standard machined step – rather than the type of steps generally found on Jacob′s ladders.
Pilothouse	An alternative term for a ship′s bridge or wheelhouse.
Pinas	Also pinis. A type of two-masted schooner with a large bowsprit, clipper bow, and transom stern built in the Terengganu area on the east coast of the Malay Peninsula.
Pinnace	1. (ship's boat) A small, light boat propelled by oars or a sail, used as a tender to larger vessels during the Age of Sail. 2. (full-rigged pinnace) A small "race built" galleon, square-rigged with either two or three masts.
Pintle	The pin or bolt on which a ship's rudder pivots. The pintle rests in the gudgeon.
Pipe (bos'n's)	Also bosun's call. A whistle used by boatswains (bosuns or bos'ns) to issue commands. Consisting of a metal tube that directs the breath over an aperture on the top of a hollow ball to produce high-pitched notes. The pitch of the notes can be changed by partly covering the aperture with the finger of the hand in which the pipe is held. The shape of the instrument is similar to that of a smoking pipe.
Pipe down	A signal on the bosun's pipe to signal the end of the day, requiring lights (and smoking pipes) to be extinguished and silence from the crew.
Piping the side	A salute on the bosun's pipe(s) performed in the company of the deck watch on the starboard side of the quarterdeck or at the head of the gangway, to welcome or bid farewell to the ship's captain, senior officers, and honored visitors.
Piracy
Pirate	One who engages in an act of piracy.
Pitch	A vessel's motion, rotating about the beam/transverse axis, causing the fore and aft ends to rise and fall repetitively.
Pitchpole	To capsize a boat stern over bow, rather than by rolling over.
Pivoting	To turn a sailing barge in shallow water by dropping the leeboard so it drags in the mud, then putting the helm hard over. The maneuver is often used to enter congested harbors.
Plane	To skim over the water at high speed rather than push through it.
Platings	The hull structure comprises joined plates whose thickness depends on vessel type and size. As expected, larger ships have heavier scantlings of plates, and smaller vessels have lower values. The plating thickness also depends on the location. ... (more at Platings)
Plimsoll line	Also National Load Line. A special marking, positioned amidships, that indicates the draft of the vessel and the legal limit to which the vessel may be loaded for specific water types and temperatures.
Plotting room	See transmitting station.
Point	A unit of bearing equal to the angle made by 1⁄32 of a circle, i.e. 11.25 degrees. A turn of 32 points is a complete turn through 360 degrees.
Point up	Also head up. To change the direction of a sailboat so that it is more upwind, i.e. to bring the bow windward. This is the opposite of falling off.
Points of sail	The course of a sailing vessel in relation to the direction of the wind, divided into six points: in irons (pointed directly into the wind), close hauled (sailing as close into the direction of the wind as possible), close reach (between close hauled and beam reach), beam reach (perpendicular to the wind), broad reach (wind behind the vessel at an angle), and running downwind, running before the wind, or simply running (wind directly behind the vessel).
Polacca
Polacca-settee	A three-masted polacca.
Polacre	Another name for a polacca.
Polacre-xebec	A type of xebec with a square rig on her foremast, lateen sails on her other masts, a bowsprit, and two headsails. A polacre-xebec differed from a felucca in that a felucca had only lateen sails.
Pollution control	Sulfur emission ... (more at Pollution control)
Pontoon	A flat-bottomed vessel used as a ferry, barge, or car float, or a float moored alongside a jetty or a ship to facilitate boarding.
Poop deck	A high deck on the aft superstructure of a ship.
Pooped	1. (of a ship or boat) to have a wave break over the stern when traveling with a following sea. 2. (colloquially) Exhausted.
Port	1. (facility): A maritime facility on a sea coast, in an estuary, or on a river with loading areas at which a vessel can bring aboard or discharge cargo or passengers. 2. A place along a coast or riverbank where a vessel can take shelter, often including loading and unloading facilities for vessels.
Port and Harbor Design	An marine engineer may also deal with the planning, creation, expansion, and modification of port and harbor designs. Harbors can be natural or artificial and protect anchored ships from wind, waves, and currents. [31] Ports can be defined as a city, town, or place where ships are moored, loaded, or unloaded. Ports typically reside within a harbor and are made up of one or more individual terminals that handle a particular cargo including passengers, bulk cargo , or containerized cargo . [32] Marine engineers plan and design various types of marine terminals and structures found in ports, and they must understand the loads imposed on these structures over the course of their lifetime. ... (more at Port and Harbor Design)
Port of registry	The port listed in a vessel's registration documents and lettered on her stern. Often used incorrectly as a synonym for home port, meaning the port at which the vessel is based, but it may differ from the port of registry.
Port tack	When sailing with the wind coming from the port side of the vessel. Vessels on port tack must give way to those on starboard tack.
Porthole	Also simply port. An opening in a ship's side, especially a round one for admitting light and air, fitted with thick glass and, often, a hinged metal cover, used as a window.
Portolan	An obsolete form of nautical chart used prior to the development of lines of latitude and longitude that indicated distances and bearing lines between ports.
Position light	An alternative term for navigation light.
Post ship	This British term was used from the second half of the 18th century until 1817 for a sixth rate ship-rigged sailing warship armed with 20 to 26 guns, smaller than a frigate but large enough to require a post-captain as her commanding officer.
Post-captain	An obsolete alternative form of the rank of captain in the Royal Navy; once achieved, promotion thereafter was entirely due to seniority.
Powder hulk	A hulk used to store gunpowder.
Powder magazine	A small room/closet area in the hull of the ship used for storing gunpowder in barrels, or "kegs", usually located centrally so as to have easy access to the grated loading area. Sometimes may be an enclosed closet with a door, so it can be locked and only the captain would have the key, similar to how rum is stored.
Pratique	The license is given to a ship to enter port on assurance from her captain that she is free from contagious disease. A ship can signal a request for pratique by flying a square solid-yellow flag. The clearance granted is commonly referred to as free pratique.
Predreadnought	A term used retrospectively after 1906 for a wide variety of steam battleships built between the 1880s and c. 1905 designed with only a few large guns for long-range fire, relying on an intermediate secondary battery used at shorter ranges for most of their offensive power, and having triple-expansion steam engines. They were rendered obsolete by the revolutionary dreadnought battleships, which began to appear in 1906 and differed from predreadnoughts in having steam turbine propulsion and an "all-big-gun" armament layout in which the ship's primary gun power resided in a primary battery of its largest guns intended for use at long range, with other gun armament limited to small weapons intended for close-range defense against torpedo boats and other small warships.
Press gang	Formed body of personnel from a ship of the Royal Navy (either a ship seeking personnel for its own crew or from a "press tender" seeking men for a number of ships) that would identify and force ("press") men, usually merchant sailors, into service on naval ships, usually against their will.
Pressure Housings	are used to enclose electronics underwater. There are two primary types of housings. Pressure compensated housings are fluid filled and are maintained at ambient pressure. A flexible diaphragm is typically used to transmit the external pressure to inside the housing. Benign substances such as mineral oil or silicone oil are used for the compensating fluid which must completely fill the inside of the housing leaving no air pockets. Components that are air or gas filled cannot be used, because they will implode under pressure. ... (more at Pressure Housings)
Preventer	Also gybe preventer and jibe preventer. A sail control line originating at some point on the boom leading to a fixed point on the boat's deck or rail (usually a cleat or pad eye) used to prevent or moderate the effects of an accidental jibe.
Principal Naval Transport Officer
Principal Warfare Officer (PWO)	One of a number of Warfare branch specialist officers.
Prison ship	Also prison hulk. A vessel used as a prison, often to hold convicts awaiting transportation to penal colonies; particularly common in the British Empire in the 18th and 19th centuries.
Private ship	In British usage, a commissioned warship in active service that is not being used as the flagship of a flag officer. The term does not imply in any way that the ship is privately owned.
Privateer	Also a private man of war. A privately owned ship authorized by a national power (by means of a letter of marque) to conduct hostilities against an enemy.
Prize	A property captured at sea in virtue of the rights of war, e.g. an enemy warship or merchant vessel.
Prize crew	Members of a warship's crew assigned to man a vessel taken as a prize.
Promenade deck	An open-air upper deck of a passenger ship on which passengers can stroll or relax.
Propeller	1. (fixed) A propeller mounted on a rigid shaft protruding from the hull of a vessel, usually driven by an inboard motor. 2. (folding) A propeller with folding blades, furling to reduce drag on a sailing vessel when not in use.
Propeller walk	Also prop walk. The tendency for a propeller to push the stern sideways. In theory, a right-hand propeller in reverse will walk the stern to port.
Prow	1. The forwardmost part of a vessel′s bow above her waterline. 2. An alternative term for the bow of a vessel, sometimes used poetically.
Puddening	Fibers of old rope packed between spars or used as a fender.
Pulling	Of an oar, as used at sea, using an oar for propulsion of a boat where each person (of several) uses one oar. This contrasts with rowing (at sea), where each person uses two oars, one each side of the boat. See row for a full explanation of the complexities of the strict definitions.
Pump boat	An outrigger canoe powered by a small gasoline engine or diesel engine, used in the Philippines and by Sama-Bajau migrants and refugees in Sabah and eastern Indonesia.
Punt	A flat-bottomed boat with a square-cut bow designed for use in small rivers or other shallow water and typically propelled by pushing against the riverbed with a pole. In this way it differs from a gondola, which is propelled by an oar.
Punting	Boating in a punt.
Purchase	A mechanical method of increasing force, such as a tackle or lever.
Purser	The person who buys, stores, and sells all stores on board ships, including victuals, rum, and tobacco. Originally a private merchant, latterly a warrant officer.
QSCS
Quarter	Designation for the aft part of the ship between 120° and 180° to starboard (the starboard quarter), or 180° and 240° to port (the port quarter).
Quarterdeck	The aftermost deck of a warship. During the Age of Sail, the quarterdeck was the preserve of the ship's officers.
Quartering sea	Seas approaching a vessel from between 105° and 165° to port or starboard. Aft of a beam sea and abeam of a following sea.
Quartermaster	1. In merchant marine usage, the seaman responsible for steering a ship. In naval usage, additional duties in running the ship's routine are included. 2. US Navy enlisted rating (QM) who, in addition to the above duties, assists with the navigation of the ship.
Quay	1. A stone or concrete structure on navigable water used for loading and unloading vessels, generally synonymous with a wharf, although the solid foundations of a quay contrast with the closely spaced piles of a wharf. When "quay" and "wharf" are used as synonyms, the term "quay" is more common in everyday speech in the United Kingdom, many Commonwealth countries, and the Republic of Ireland, while "wharf" is more commonly used in the United States. 2. To land or tie up at a quay.
Quayside	1. An area alongside a quay. 2. Being alongside a quay, e.g. "The ship is moored quayside."
Queen's Regulations	Also King's Regulations. The standing orders governing the British Royal Navy issued in the name of the current Monarch.
Quickwork	Also lining. The ceiling inside the hull above the turn of the bilge, usually being of lighter dimensions than the ceiling lower down (spirketting).
Quirk Waveskimmer Kite (QWK)	Abbreviated as QWK (Pronounced “Quick”), this is a type of high speed cargo and passenger transport vessel that applies Wing-In-Ground-Effect principles to lift heavy loads above the waves and accelerate them to light aircraft speeds. This vessel facilitates rapid cargo and passenger transport services for seastead communities located hundreds or even thousands of miles apart. See Flyship.
Quoin	A wedge used to assist in the aiming of a cannon
ROVs	or Remotely Operated Vehicles are underwater robots used for a wide variety of tasks, ranging from simple inspection to maintenance and repair work. These tasks are performed on offshore oil rigs, ship hulls, docks, mooring buoys, dams, bridges and power plants, and in water tanks. ROVs are lowered on a cable either alone or in a protective cage and then operated on a slack tether that decouples it from the ship’s surface motion. Video cameras serve as “eyes” for the operator who controls the vehicle via the cable. An ROV can explore, take photographs, collect samples, or handle instruments, operating around the clock for many consecutive days. Job-specific tool skids are sometimes mounted under larger vehicles. A good write up on ROVs and their history may be found at the MTS ROV committee Web site http://www.rov.org/info.cfm .
Rabbet	Also rebate. A groove cut in wood to form part of a joint.
Radar	An electronic system designed to transmit radio signals and receive reflected images of those signals from a "target" in order to determine the bearing and distance to the target. The term is an acronym for RAdio Detection And Ranging.
Radar reflector	A special fixture fitted to a vessel or incorporated into the design of certain aids to navigation to enhance their ability to reflect radar energy. In general, these fixtures materially improve the visibility for use by vessels with radar.
Raft	A flat structure used for support or transportation over water, lacking a hull and kept afloat by buoyant materials or structures such as wood, balsa, barrels, drums, inflated air chambers such as pontoons, or extruded polystyrene blocks.
Raft ship	Another name for a disposable ship.
Rail meat	A term used to describe the members of a sailboat crew that are using their body weight to control the angle of heel of the boat.
Rake	To incline from the perpendicular; something so inclined is said to be raked or raking (e.g. a stem, stern, mast, funnel, etc.).
Ram	1. A weapon consisting of an underwater prolongation of the bow of a vessel to form an armored beak, intended to be driven into the hull of an enemy vessel in order to puncture the hull and disable or sink that vessel. 2. An armored warship of the second half of the 19th century designed to use such a weapon as her primary means of attack.
Range	1. To lay out a rope or chain on deck in a zig-zag or (for rope) a figure‐eight pattern (as opposed to in a coil) so that it can run freely. The zig-zag pattern may be described as flakes. 2. The difference between the heights of the high and low tides – a figure that will vary from place to place and day to day.
Range clock	A clockwork device used aboard a warship to continuously calculate the distance or range to an enemy ship.
Range lights	See leading lights.
Rating	Also rate or bluejacket. 1. In British usage, a junior enlisted member of a country's navy; i.e., any member of the navy who is not an officer or warrant officer.
Ratlines	Also rattlins or ratlins. The rungs fastened between the shrouds permanently rigged from bulwarks and tops to the mast to form rope ladders enabling access to the topmasts and yards.
Razee	1. A sailing ship that has been cut down to reduce the number of decks. 2. To cut down a sailing ship to reduce the number of decks.
Reach	1. A section of a stream or river along which similar hydrologic conditions exist, such as discharge, depth, area, and slope. 2. In sailing usage, a straight section of water that can be traversed in a single reaching maneuver, without tacking.
Reaching
Reaching sail
Ready about	A call to indicate imminent tacking. See also going about.
Receiver of Wreck	A government official whose duty is to give owners of shipwrecks the opportunity to retrieve their property and ensure that law-abiding finders of wrecks receive an appropriate reward.
Receiving hulk	Also receiving ship. A hulk used in harbor to house newly recruited sailors before they are assigned to a crew.
Red Duster	A traditional nickname for the Red Ensign, the civil ensign flown by civilian vessels of the United Kingdom.
Red Ensign	Also Red Duster. A British flag flown as an ensign by certain British ships. Since 1854, it has been flown by British merchant ships (except for those authorized to fly the Blue Ensign) as the United Kingdom′s civil ensign. Prior to 1864, ships of the Royal Navy′s Red Squadron also flew it, but its naval use ended with the reorganization of the Royal Navy in 1864.
Red Right Return	A phrase used as a mnemonic to remember that the navigational standard for a vessel entering ("returning to") a port in the Americas (excluding Greenland), Japan, South Korea, and the Philippines is for her to steer so that red-marked navigational aids lie to starboard (to the "right") of an observer facing forward on the vessel, while green-marked aids must lie to port (i.e. to the "left"). This contrasts with the rest of the world, where the standard is the opposite, i.e. green markers must lie to starboard and red ones to port.
Red-to-red	A passage of two vessels moving in the opposite direction on their port sides, so called because the red navigation light on one of the vessels faces the red light on the other vessel.
Reef	1. (noun) Rock or coral that is either partially submerged or fully submerged but shallow enough that a vessel with a sufficient draft may touch or run aground. 2. (verb) To temporarily reduce the area of a sail exposed to the wind, usually to guard against adverse effects of strong wind or to slow the vessel.
Reef-bands	Long pieces of rough canvas sewn across the sails to give them additional strength.
Reef-points	Lengths of rope attached to a sail and used to tie up the part of a sail that is taken out of use when reefed. In older systems, such as square or gaff rigs, the reef points take some of the load on the sail and distribute it to the boltrope; with slab reefing, the reef-points just keep the sail fabric controlled in a tidy manner. Reef points may either be sewn to each side of the sail or passed through eyelets.
Reef-tackles	Ropes employed in the operation of reefing.
Reefer ship	Also simply reefer. 1. A refrigerated cargo ship used to carry perishable goods that require refrigeration.
Reeve	To thread a line through blocks in order to gain a mechanical advantage, such as in a block and tackle.
Regatta	A series of boat races, usually of sailboats or rowboats but occasionally of powered boats.
Regular ship	A term used by the British East India Company from the 17th to the 19th centuries for merchant ships that made "regular voyages" for the company between England (later the United Kingdom) and ports east of the Cape of Good Hope, a trade over which the company held a strict monopoly. The company chartered most of its ships; "regular ships" were those under long-term charter, and the company kept their operations under tight control. A set of "regular ships" set off for Asian ports during each sailing season (September through April), and returned up to two years later. The status and role of "regular ships" differed from that of ships the company referred to as chartered ships, country ships, extra ships, and licensed ships.
Relative bearing	A bearing relative to the direction in which the vessel is pointing or traveling; the angle between the vessel's forward direction and an object, as measured clockwise from the bow. See also absolute bearing.
Releases	A common task is to recover an object that is weighted down or anchored to the seafloor. To do this without divers or an ROV , a release is utilized. There are several types of releases. Galvanic releases rely on seawater to corrode a wire or link. Generally these are inexpensive but the rate of corrosion can differ from place to place and thus the time to release is not controlled with great precision. ... (more at Releases)
Remote Sensing	is ocean data collected by sensors on satellites or aircraft. The term implies that the sensor is placed at some considerable distance from the sensed target, in contrast to close-in measurements made by “in situ” sensing. Commonly measured parameters are ocean color, sea surface temperature and sea surface altitude. Ropes and Tension Members are used to carry loads on moorings, towed sleds and devices lowered over the sides of ships. Fiber ropes, wire ropes and chains are examples of flexible tension members. Synthetic fiber ropes are made from Nylon, Dacron, Polypropylene, Kevlar, Vectran and Spectra. Considerations in selecting a material are strength, weight/buoyancy, and stretch. Synthetic fiber ropes can be terminated by eye splicing or by socketing with epoxy. ... (more at Remote Sensing)
Repair ship	A naval auxiliary ship designed to provide maintenance support to other ships.
Replenishment oiler	A naval auxiliary ship which provides fuel and dry stores to other ships.
Research vessel	A ship designed and equipped to carry out research at sea, especially hydrographic surveys, oceanographic research, fisheries research, naval research, polar research, and oil exploration.
Reserve fleet	A collection of naval vessels fully equipped for service but partially or fully decommissioned because they are not currently needed. In the modern United States, a reserve fleet is sometimes informally called a ghost fleet. During the Age of Sail and well into the 19th century, ships in a reserve fleet were said to be in ordinary.
Rib tickler	A bargeman's name for the tiller.
Riding light	A light hung from the forestay when at anchor.
Rig	1. The arrangement of masts, sails, and rigging on a sailing vessel. 2. To fit a sailing vessel with its masts, sails or rigging.
Rigging	The system of masts and lines on ships and other sailing vessels.
Rigging chocks	Thick blocks of wood fixed outside the rails to take the chain plates for the shrouds.
Rigging screw	A bottle screw used to keep wires taut.
Righting
Righting moment	The force that tends to restore a ship to upright equilibrium once a heel has altered the relationship between the vessel's center of buoyancy and center of gravity.
Rigol	The rim or "eyebrow" above a porthole or scuttle.
Rip rap	A man-made pile of rocks and rubble used as a base to support an aid to navigation, often an offshore lighthouse.
Ro-ro	See roll-on/roll-off ship.
Roads	See roadstead.
Roadstead	Also roads. A sheltered area outside a harbor where a ship can lie safe at anchor.
Roaring Forties
Rode	Also anchor rode. The anchor line, rope, or cable connecting the anchor chain to the vessel.
Rogue wave	Any unusually large wave for a given sea state; formally, a wave whose height is more than twice the significant wave height of that sea state (i.e. the mean of the largest third of waves in a wave record).
Roll	1. The side-to-side motion of a vessel as it rotates about the fore-aft (longitudinal) axis. Listing is a lasting, stable tilt, or heel, along this longitudinal axis. 2. Another name for the longitudinal axis itself (e.g. the "roll axis").
Roll-on/roll-off ship	Also RORO or ro-ro. A vessel designed to carry wheeled cargo that can drive on and off the ship on its own wheels.
Roller	A rolling swell. Swell that has increased in height due to influence of the bottom in shallow water, but before it is high enough to break.
Rolling vang	A second set of sprit-head vangs played out forward to rail near the bows, used to give additional control and support when needed in a seaway.
Rolling-tackle	A number of pulleys, engaged to confine the yard to the weather side of a mast; this tackle is much used in a rough sea.
Romper	In a convoy, a ship that breaks ranks and "romps" ahead out of formation with the other ships.
Rope yarn	1. A period, traditionally on Wednesday afternoons, when a tailor boarded a sailing warship while the vessel was in port; the crew was excused from most duties and had light duty mending uniforms and hammocks and darning socks. When the ship was at sea, the crew similarly was excused from most duties on Wednesday afternoons to engage in mending chores. Wednesday afternoons, like Sundays, thus were a more social time when crewmen rested from normal duties, similar to a Sunday, and, because the crew used rope yarn for mending, Wednesday afternoon became known as rope yarn Sunday. 2. After uniforms began to require less care, and through the mid-20th century, a period on Wednesday afternoons when naval crew members were excused from their regular duties to run personal errands.
Ropes, the	1. All cordage; the lines in the rigging. 2. Any cordage of over 1 inch (2.5 cm) in diameter.
Round to	To turn the bow of a vessel into the wind.
Rove	Past tense of reeve.
Row	1. (in general speech) to propel a boat with oars 2. (more precisely, as used at sea) to propel a boat with oars, where each rower handles two oars, one on each side of the boat. This contrasts with the inland waters definition. When, at sea, a person is working just one oar, this is termed pulling.
Rowlock	1. The cutout in the washstrake of a boat into which an oar is placed, so providing a fulcrum when the oar is in use. 2. A common term for an oar crutch, the u-shaped metal fitting, with a pin underneath that fits in a socket in the gunwale of a boat to provide the fulcrum for an oar. See also thole pin.
Royal	1. On large sailing ships, a mast right above the topgallant mast. 2. The sail of such a mast.
Rubbing strake	An extra plank fitted to the outside of the hull, usually at deck level, to protect the topsides.
Rudder
Rudder stop	A fitting that limits the swing of the rudder.
Rudderstock	The structural part of a rudder that transmits the torque created by the tiller or steering gear to the rudder blade. It may consist of a steel tube which passes through bearings in the hull above the rudder, or with a stern-hung rudder, is the structure carrying all or some of the pintles or gudgeons on which the rudder pivots.
Ruffle	A serrated iron ring attached to the barrel of the anchor winch and to which the pawl is applied to prevent backruns of the anchor chain.
Rules	(1) Rules for the Classification of Ships or other special units;
Rum-runner	See go-fast boat.
Rummage	Also romage. 1. A place or room for the stowage of cargo in a vessel.
Rummage sale	A sale of damaged cargo (from French arrimage).
Run	1. The stern of the underwater body of a ship from where it begins to curve upward and inward. 2. A voyage, particularly a brief or routine one.
Running backstays	A backstay that can be released and moved out of the way so that it does not interfere with sails or spars on the leeward side. On tacking, the new windward running backstay must be set up promptly to support the mast.
Running before the wind	Also simply running. Sailing more than about 160° away from the direction from which the wind is blowing (i.e. moving in the same or nearly the same direction as the wind). If moving directly away from the wind, it is called a dead run. Compare reaching and beating.
Running gear	1. The propellers, shafts, struts, and related parts of a motorboat. 2. The running rigging of a sailing vessel.
Running light	An alternative term for navigation light.
Running rigging	Also running gear. Rigging used to manipulate sails, spars, etc. in order to control the movement of a sailing vessel. Contrast standing rigging.
S.B. (or SB)	Prefix for "Sailing Barge", used before a ship's name.
S.S. (or SS)	To the purist, a prefix for Screw Steamer (i.e. with screw propulsion, meaning propellers). It is used before the name of a ship. Compare with "PS", which stands for "Paddle Steamer". Widely used as an abbreviation for "Steam Ship".
S/V	An abbreviation of "Sailing Vessel", used before the ship's name.
SOG	An abbreviation of "speed over ground", the speed of the vessel relative to the Earth (and as shown by a GPS). Referenced on many fishing forums.
SONAR	1. An acronym for "SOund Navigation And Ranging", a method of using sound pulses to detect, range, and sometimes image underwater targets and obstacles or the bed of the sea. See also echo sounding and ASDIC. 2. The equipment used to conduct such searches, ranging, and imaging.
SOS	International distress signal.
STUFT	British and Commonwealth acronym for Ship Taken Up From Trade, which refers to a civilian ship requisitioned for naval or other government service.
STW	An abbreviation of "speed through (the) water"; the speed of the vessel relative to the surrounding water (and as shown by a Log). Used in navigation.
Saddle chock	A transverse beam placed over the transom with fairleads for mooring warps.
Safe harbor	A harbor that provides safety from bad weather or attack.
Safe haven	A safe harbor, including natural harbors, which provide safety from bad weather or attack.
Safety briefing	See muster drill.
Sagging
Sail	2. The power harnessed by a sail or sails to propel a vessel.
Sail drive	A non-steerable drive leg fitted through the bottom of a sailboat carrying a propeller. Compare azimuth thruster and sterndrive.
Sail loft	A large open space used by sailmakers to spread out sails.
Sail-plan	A set of drawings showing various sail combinations recommended for use in various situations.
Sailing skiff	See skiff.
Sailmaker	A craftsman who makes and repairs sails, working either on shore in a sail loft or aboard a large, ocean going sailing ship.
Sailorman	London term for a sailing barge, or a bargeman.
Sally ship
Saloon	A social lounge on a passenger ship.
Saltie	Great Lakes term for a vessel that sails the oceans.
Salty dog	Slang for a sailor, especially for a seaman in the navy.
Salvage and Recovery	Underwater salvage and recovery techniques are continuously modified and improved to find and recover shipwrecks and other valuable articles lost in the ocean. Marine engineers use their skills to assist at every stage of this process – from the planning of searches, to the documentation of wreck sites, to the physical recovery of entire vessels, artifacts, or parts thereof. Numerous famous examples of shipwrecks exist, but recoveries include Squalus (subsequently rechristened USS Sailfish (SS-192) ) and Project Azorian, the clandestine recovery of a portion of Soviet submarine K-219 by the U.S. Navy and CIA in 1974 aboard Glomar Explorer . [33] [34] ... (more at Salvage and Recovery)
Salvage tug	Sometimes called a wrecking tug. A specialized tugboat used to assist ships in distress or in danger of sinking, or to salvage ships which have already sunk or run aground.
Salvor	A person engaged in the salvage of a ship or items lost at sea.
Sampan	A relatively flat-bottomed Chinese wooden boat from 3.5 to 4.5 meters (11 to 15 ft) long, generally used in coastal areas or rivers and as traditional fishing boats. Some have a small shelter, and they may be used as a permanent habitation on inland waters. It is unusual for sampans to sail far from land as they are not designed to survive rough weather.
Sampson post	A strong vertical post used to fasten the anchor cable or mooring warps, for towing another vessel, or to support a ship's windlass, the heel of a ship's bowsprit, the base of a cargo derrick or any other heavy load. In a smaller vessel, is usually fastened to the keel at its lower end.
Sandsucker	A barge that collects sand from the bottom of lakes.
Scandalize	To reduce the area and efficiency of a sail by expedient means (slacking the peak and tricing up the tack) without properly reefing, thus slowing boat speed. Also used in the past as a sign of mourning.
Scantling	In shipbuilding , the scantling refers to the collective dimensions of the framing [1] (apart from the keel ) to which planks or plates are attached to form the hull. [2] The word is most often used in the plural to describe how much structural strength in the form of girders, I-beams, etc., is in a given section. The scantling length refers to the structural length of a ship. ... (more at Scantling)
Scantlings	Dimensions of a ship's structural members, e.g. frame, beam, girder, etc.
Schooner	A type of sailing vessel characterized by the use of fore-and-aft sails on two or more masts with the forward mast being no taller than the rear masts. First used by the Dutch in the 16th or 17th century. A topsail schooner has a square topsail (and may also have a topgallant) on the foremast.
Schooner barge	A type of barge either converted from a schooner or purpose-built as a barge with a schooner rig, primarily in use from the 1860s to the 1940s, initially on the Great Lakes and later in salt-water environments as well. A schooner barge required a smaller crew than a schooner and needed to be towed, but under favorable conditions could hoist sails to reduce fuel consumption by the vessel towing her.
Schuyt	Another name for a Dutch barge.
Scope	The length of cable extended when a ship rides at anchor.
Scour	is the destructive effect that flowing water has on a submerged object. When a manmade object such as a bridge pier, pipeline, cable, etc. is submerged in flowing water, the local effect is to increase the current velocity around the object. This increased velocity has the tendency to remove or scour away the bottom material that supports the structure.
Scow	1. A method of preparing an anchor for tripping by attaching an anchor cable to the crown and fixing to the ring by a light seizing (also known as becue). The seizing can be broken if the anchor becomes fouled. 2. A type of clinker dinghy, characteristically beamy and slow.
Scow schooner
Scow sloop
Screaming Sixties	Also called the Shrieking Sixties. Strong westerly winds found in the Southern Hemisphere, south of 60 degrees. They are stronger than the similar "Roaring Forties" to their north.
Screecher	A specialty sail which can be used as an upwind genoa sail, reaching sail, or downwind sail. The name comes from combining "spinnaker" and "reaching".
Screw	1. A propeller. 2. Propeller-driven (e.g. a screw frigate or screw sloop).
Scud	A name given by sailors to the lowest clouds, which are mostly observed in squally weather.
Scudding	A term applied to a vessel when carried furiously along by a tempest.
Scull	1. (v.) In sport or recreational rowing, especially on inland water, to propel a boat by oars, where each of one or several persons uses two oars, one on each side of the boat. This contrasts with the maritime traditional working boat or naval usage, where this activity is called rowing. 2. (v.) To propel a boat with a single oar resting in a notch at the stern, using a figure of eight motion of the blade of the oar, which is continuously immersed in the water
Scuppers	Originally a series of pipes fitted through a ship's side from inside the thicker deck waterway to the topside planking in order to drain water overboard, with larger quantities drained through freeing ports, which were openings in the bulwarks.
Scuttle	1. A small opening, or lid thereof, in a ship's deck or hull. 2. To sink a vessel deliberately.
Scuttlebutt	1. A barrel with a hole in it, used to hold water that sailors would drink from. By extension (in modern naval usage), a shipboard drinking fountain or water cooler. 2. Slang for gossip.
Scuttling	Making a hole in the hull of a vessel or opening seacocks, especially in order to sink a vessel deliberately.
Sea	1. The ocean. 2. A body of salt water smaller than an ocean and generally forming part of, or connecting with, an ocean or a larger sea.
Sea anchor	A stabilizer deployed in the water for heaving to in heavy weather. It acts as a brake and keeps the hull in line with the wind and perpendicular to the waves. Often in the form of a large bag made of heavy canvas. See also drogue.
Sea chest	A watertight box built against the hull of the ship communicating with the sea through a grillage, to which valves and piping are attached to allow water in for ballast, engine cooling, and firefighting purposes. Also, a wooden box used to store a sailor's effects.
Sea shanty/chanty/chantey	Work song to accompany rhythmical labor.
Sea state	The general condition of the free surface on a large body of water with respect to wind waves and swell at a certain location and moment, characterized by statistics, including the wave height, period, and power spectrum. The sea state varies with time, as the wind conditions or swell conditions change.
Sea trial	The testing phase of a boat, ship, or submarine, usually the final step in her construction, conducted to measure a vessel's performance and general seaworthiness before her owners take delivery of her.
Sea-kindly	(of a boat or ship) Having a comfortable motion in rough seas
Seaboat	1. A ship's boat kept ready for immediate use at sea, and used, for example, for retrieving a man overboard, or taking a boarding party to another vessel. Usually rigged with patent disengaging gear that allows both falls to be released simultaneously and quickly, so enabling the boat to be launched from a ship with way on. 2. A term used for any vessel when assessing her physical behavior at sea. A vessel that performs well in challenging weather or sea conditions such as heavy seas is a good seaboat, while one which does not is a bad seaboat.
Seaboots	High waterproof boots for use at sea. In leisure sailing, known as sailing wellies.
Seacock
Seakeeping	The ability of a watercraft to remain seaworthy in the conditions she encounters while underway. A vessel with a good seakeeping ability is very seaworthy even in rough weather.
Sealer	A vessel designed for or engaged in seal hunting.
Sealing	1. The hunting of seals. 2. The caulked floor of the hold. Also ceiling.
Seals	: The type of seals discussed here are not marine mammals or navy commandos. Seals are a means for keeping water out of pressure housings . Types of seals used in the marine environment include gaskets, shaft seals, lip seals, stuffing tubes and gland seals. The o-ring is the most commonly-used type of seal underwater. It is a solid piece of elastomeric material shaped like a doughnut or torus. When pressed between mating surfaces, an o-ring blocks the passage of liquids or gases. The oring is the most widely used seal due to its simplicity, low cost, ease of installation, and small space requirements without supporting structures. An O-ring can be considered an incompressible viscous fluid with very high surface tension. This “fluid” is forced by mechanical or hydraulic pressure to flow into the sealing cavity, blocking the flow of the lessviscous fluid being sealed. Properly installed, the O-ring is squeezed about 10% to 15% of its original cross-sectional diameter. The compression absorbs the tolerance stack up between mating surfaces (or between shaft and gland in dynamic applications) and forces the elastomer into microscopic surface grooves on mating parts. Successful use of o-rings depends upon proper groove dimensions and selection of the right elastomeric compound. Compounds are chosen for their resistance to chemicals and temperatures. Common materials utilized include Nitrile, neoprene, flurocarbon (Viton), silicone, fluorosilicone, and urethane. ... (more at Seals)
Seaman	A generic term for a sailor, or (part of) a low naval rank.
Seamount	A large geologic landform rising from the ocean floor that does not reach the surface; an underwater mountain.
Seaworthy	Certified for and capable of safely sailing at sea.
Second mate	Also called a second officer. A licensed member of the deck department of a merchant ship, third – or, on some ocean liners, fourth – in command; a watchkeeping officer, customarily the ship's navigator. Other duties vary, but the second mate is often the medical officer and in charge of maintaining distress-signaling equipment. On oil tankers, the second mate usually assists the chief mate with tank-cleaning operations.
Sediment Traps	are used to collect samples of particles sinking through the water column. Scientists can learn the rate of sedimentationand about the organisms that populate the water column using sediment traps.
See you on the one - CUOTO	Used principally by Pilot's and River Tug and Barge deck and Officer crew as (a) a friendly farewell (similar to the phrase "catch you later") or (b) more properly used in vessel to vessel VHF (or when needed ship's whistle) communication, along with its companion phrase "see you on the two" to indicate which side a head-to-head vessel crossing is going to occur. The correct response to the challenge is to repeat it back to the apposing vessel in agreement, and if not in agreement to ask for an alternative arrangement. The "on the one" indicates a single whistle sound signal, or port to port crossing, whilst "on the two" is a dual (two) whistle sound signal, or starboard to starboard crossing. In the USA, a "one whistle" or port to port crossing is the normal and preferred crossing side.
Seekers	London term for sailing barges that sought cargo, carrying cargo for other merchants at a fee, rather than for the owner.
Seiner	A fishing vessel rigged to fish by seining.
Seize	To bind two ropes together with small line.
Self-sustaining
Self-unloader	Great Lakes slang term for a vessel with a conveyor or some other method of unloading the cargo without shoreside equipment.
Semi-dreadnought	An advanced type of predreadnought battleship of the very early 20th century with an "all-big-gun" armament of mixed calibers. A semi-dreadnought differed from a conventional predreadnought, which had only a few large guns for long-range fire and relied on an intermediate secondary battery used at shorter ranges for most of her offensive power, but also differed from a dreadnought battleship, which dispensed with an intermediate secondary battery in favor of an all-big-gun main battery of the same caliber for use at long range. A semi-dreadnought had greater firepower at longer ranges than a conventional predreadnought, but lacked the long-range firepower of a dreadnought.
Sennet	Cord formed by plaiting rope-yarn by hand. There are many types of plait, which may be flat, round, or square in section, and many uses.
Serve	Cover a rope or splice by wrapping with thin line to protect it. Compare with whipping.
Services	The activities rendered by the Society upon request that are made by or on behalf of the Interested Party.
Set	The direction toward which the current flows.
Settle	(of a ship or boat): sink lower in the water, often prior to sinking altogether.
Sextant	A navigational instrument used to measure a ship's latitude.
Shackle	U-shaped iron, with a screw pin at the open end used for securing stays to sails, allowing easy removal.
Shaft	1. A propeller shaft. The term shaft can be used instead of "propeller" to describe the number of propellers a ship has, e.g., The ship has two shafts or The ship's engines drive three shafts. 2. To push or propel (a boat) with a pole.
Shaft Lines
Shaft alley	The section of a ship that houses the propulsion shaft, running from the engine room to the stuffing box.
Shaft log	A shaped piece of timber or metal fitted to a vessel's deadwood, keel, or keelson at the point where the stern tube passes through the hull.
Shakedown cruise	Also simply called a shakedown. A cruise performed before a ship enters service or after major changes such as a crew change, repair, or overhaul during which the performance of the ship and her crew are tested under working conditions.
Shakes	Pieces of barrels or casks broken down to save space. They are worth very little, leading to the phrase "no great shakes".
Shallop	1. A term used for a variety of boats and small ships used for coastal navigation beginning in the 17th century. 2. A large boat armed with cannon used by the Danes as gunboats during the Gunboat War (1807–1814).
Shanghaied	The condition of a crewman involuntarily impressed into service on a ship.
Sheave	(traditionally pronounced "shiv"). The wheel in a block, which rotates as the rope runs.
Sheave-hole	A hole or slot in a spar, fitted with a sheave to allow a rope to run.
Sheer	The upward curve of a vessel's longitudinal lines as viewed from the side.
Sheer line	The intersection of the external hull surface and the main deck surface, shown by a line on the sheer plan.
Sheer plan	In shipbuilding, a diagram showing an elevation of the ship's sheer viewed from the broadside.
Sheerstrake
Sheet	A rope attached to the clew and used to control the setting of a sail in relation to the direction of the wind. The sheet is often passed through a tackle before being attach to fixed points on the deck, or in the case of a barge, to a traveler on the main horse.
Sheet anchor	Historically, the heaviest anchor aboard a sailing ship, to be used only in case of emergency, and located amidships. In more general usage, the term has come to mean a person or thing that is very reliable in times of emergency. For example, during the first inauguration of Thomas Jefferson, he advocated, "the preservation of the General [Federal] Government in its whole constitutional vigor, as the sheet anchor of our peace at home and safety abroad."
Sheet bend	A bend to attach a rope to a small eye or clew, e.g. to attach a hammock to a clew or a painter to the Jacobs Ladder.
Shell	Also called a fine boat in the United Kingdom. An extremely narrow, and often disproportionately long, rowing boat outfitted with long oars, outriggers to hold the oarlocks away from the boat, and sliding seats, specifically designed for racing or exercise.
Shelter deck	An upper deck having no overhead protection from the weather itself, but sheltering the deck below it.
Shift colors	1. Changing the flag and pennant display when a moored vessel becomes underway, and vice versa. A highly coordinated display that ships take pride in; the desired effect is that of one set of flags vanishing while another set flashes out at precisely the same time. 2. Slang for changing out of one's Navy uniform into civilian clothes to go ashore. (The US Navy's newsletter for retired personnel is nicknamed Shift Colors for this reason).
Shift tides	Sighting the positions of the Sun and Moon using a sextant, using a nautical almanac to determine the location and phase of the Moon, and calculating the relative effect of the tides on the navigation of the ship.
Ship	1. (n.) Strictly, a sailing vessel of three-masts or more and square-rigged on all masts. 2. (n.) More generally, any medium or larger seagoing vessel. Smaller vessels or those used in sheltered waters are generally called boats. Exceptions include submarines which are always referred to as boats.
Ship Taken Up From Trade	See STUFT.
Ship a sea	(Of a ship or boat): be flooded by a wave.
Ship breaking	Also called ship cracking, ship demolition, ship dismantling, or ship recycling. The demolition of ships for spare parts and scrap metal. A ship on her way to be scrapped is said to be going to the breakers.
Ship cemetery	Another name for a ship graveyard.
Ship classification society (Society)	Also ship classification organization or ship classification organization. A non-governmental organization that establishes and maintains technical standards for the construction and operation of ships and offshore structures.
Ship graveyard	Also called a ship cemetery. 1. A location where the hulls of discarded ships are left to decay and disintegrate.
Ship over	To reenlist. When a sailor extends his or her service another term.
Ship rig	See full-rigged ship.
Ship sloop	A type of sloop-of-war introduced in the 1740s that had three square-rigged masts (in contrast to the brig sloop introduced in the 1770s, which had two masts).
Ship stores	The materials, supplies and equipment required for the navigation, maintenance, operation and upkeep of a ship.
Ship's bell	Striking the ship's bell is the traditional method of marking time and regulating the crew's watches. Each bell (from one to eight) represents a 30-minute period since the beginning of a four-hour watch. For example, in the classical system, "Three bells in the morning watch" represents 90 minutes since the beginning of the morning watch, or 5:30 AM. "Eight bells" indicates the end of a watch.
Ship's biscuit	See hard tack.
Ship's company	The crew of a ship.
Ship's complement	The number of persons in a ship's crew, including officers.
Ship's husband	A legal term for an agent based on land, who has authority to make repairs and attend to the management, equipment, and general management of a ship in the home port.
Ship-of-the-line	A type of sailing warship constructed from the 1600s through the mid-1800s to serve as part of the line of battle; one of the largest and most powerful warships of the era.
Ship-polacca	A three-masted polacca.
Shipbreach	Another name for a shipwreck.
Shipping	1. Passage or transport on a ship; maritime transport. 2. The body of ships belonging to one country, port, or industry.
Ships husbandry	All aspects of maintenance, cleaning, and general upkeep of the hull, rigging, and equipment of a ship. It may also be used to refer to aspects of maintenance which are not specifically covered by the technical departments.
Shipwreck	1. The remains of a ship that has sunk. 2. The remains of a ship that has run aground such that she is no longer seaworthy.
Shipwrecked	A person marooned due to the loss of a ship he or she was aboard is said to be shipwrecked.
Shipwrecking	To wreck a ship through a mishap.
Shipwright	A person who designs, builds, and repairs ships, especially wooden ones.
Shipyard	A facility where ships or boats are built and repaired. Routinely used as a synonym for dockyard, although dockyard is sometimes associated more closely with a facility used for maintenance and basing activities, while shipyard sometimes is associated more closely with a facility used in construction.
Shoal	Shallow water that is a hazard to navigation.
Shoal draught	An especially shallow draught on a vessel, making the vessel capable of sailing in unusually shallow water.
Shore leave	Free time given to officers and crew of a naval vessel when they are off duty and allowed to disembark and spend time on land. See also liberty.
Short stay	The relative slackness of an anchor chain; "short stay" means the chain is somewhat slack, and neither vertical nor fully extended.
Shorten	1. To take in the slack of (a rope). 2. To reduce (sail) by taking it in, e.g. "shorten sail".
Shot across the bow	A shot fired close to and in front of a moving vessel to warn her to stop, often for boarding.
Shrieking Sixties	See screaming Sixties.
Shrimper	A fishing vessel rigged for shrimp fishing.
Shroud	A rope or cable serving to support a mast from either side.
Shrouds	Standing rigging running from a mast to the sides of a ship to support the mast sideways. The shrouds work with the stays, which run forward and aft, to support the mast's weight.
Sick bay	A compartment reserved for medical purposes.
Sideboy	One of an even-numbered group of seamen posted in two rows on the quarterdeck when a visiting dignitary boards or leaves the ship, historically to help (or even hoist) him aboard.
Sidewheel	1. A side-mounted paddle wheel used for propulsion by a paddle steamer. 2. Propelled by sidewheels (e.g. "sidewheel steamer").
Sidewheeler	A paddle steamer propelled by a pair of paddle wheels, one mounted on each side.
Single Bottom and Double Bottom Structure	Like single and double hull, a vessel can be a single bottom, for smaller ships, or double bottom, for larger vessels. For double bottoms, an inner shell plating is present at a certain height above the lowermost bottom shell for bolstering strength and protection against flooding. Now, all double hull structures are double-bottom as well, as obvious. However, all double-bottom vessels are not double-hull and may be single-hull at all other places!
Single and Double Hull	Vessels have either single or double hulls, like most tankers. The double hull has an external plating system followed by an internal plating system parallel to the outer shell. This is primarily to enhance the strength of the hull and offer protection for structural damages. The spaces between the two hulls on the sides may store ballast, fuel, or bilge water. The inner and outer shells of plating are joined by interspersing structural members.
Single up	To reduce the number of mooring lines to a minimum immediately prior to getting under way. In a small vessel this would usually be a reduction to a mooring line at just the bow and the stern. In a larger vessel this may be a reduction to headrope, stern rope and two springs.
Single-banked	(of the arrangement of oars on a boat) having only one oarsman seated on each thwart, operating one oar on one side of the boat, with the oars alternating between port and starboard along the length of the boat. This contrasts with double-banked, where two oarsmen are seated on each thwart, each of whom operates one oar on their side of the boat. A third arrangement is to have one rower on each thwart working two oars, one on each side of the boat.
Siren	A sound signal that uses electricity or compressed air to actuate either a disc or a cup-shaped rotor.
Sister ship
Skaffie	A type of small sailing vessel used for fishing, primarily during the 19th century and mostly in the Moray Firth region of Scotland.
Skeg	A downward or sternward projection from the keel in front of the rudder. Protects the rudder from damage, and in bilge keelers may provide one "leg" of a tripod on which the boat stands when the tide is out.
Skeleton crew	A minimal crew, usually employed during an emergency or when a vessel is inactive, generally consisting of the minimum number of personnel required to maintain or operate the vessel.
Skiff	A small boat, traditionally a coastal or river craft, for leisure or fishing, with a single person or small crew. Sailing skiffs have developed into high-performance competitive classes.
Skipjack	A type of sailboat used as a traditional fishing boat on the Chesapeake Bay for oyster dredging. It arose around the end of the 19th century as the successor to the bugeye as the chief oystering boat on the bay.
Skipper	The captain of a ship.
Skysail	A square sail set above the royals, typically only carried by large barques and ships, such as the Primrose Hill (1885), Oweenee (1819), and Mushkosa (1819).
Skyscraper	A small triangular sail above the skysail. Used in light winds on a few ships.
Slack tide	The period between rising tide and falling tide, or the period between falling tide and rising tide when there is no tidal-induced current.
Slamming
Slave ship	A large cargo ship specially converted for the transportation of slaves in the slave trade. Also known as a slaver or Guineaman, the latter term deriving from the Guinea coast of West Africa.
Slaver	Another name for a slave ship.
Slide	The cabin hatch on a barge.
Sliding Feet
Sling	1. To pass a rope around something in preparation for attaching a hoisting or lowering tackle to it. 2. A band of rope or iron for securing a yard to a mast; chiefly used in the plural, slings.
Slip	1. To let go a rope at a precise moment, such as when releasing the last attachment to a buoy, when getting underway. 2. To slip an anchor: to let go the anchor cable, abandoning the anchor so as to get under way in an emergency, rather than spend time hauling in the cable to raise the anchor in the normal way. The released anchor cable is usually buoyed to aid recovery later.
Slip Rings	are electromechanical devices that allow the transmission of power and electrical signals from a stationary to a rotating structure. Also called a rotary electrical joint, collector or electric swivel, a slip ring can be used in any electromechanical system that requires unrestrained, intermittent or continuous rotation while transmitting power and/or data. They are commonly used on cable winches . For fiber optic conductors the Fiber Optic Rotary Joints (FORJs) are used in place of slip rings.
Slip rope	A mooring rope that is intended to be the last to be released when getting under way and is arranged so that it can be released from on-board. An example of this would be a rope that is led from the ship (or boat), through a ring on a mooring buoy, and then back to the ship.
Slipway
Sloop	In modern usage (from circa 1850s), a single-masted fore and aft sailing rig with one headsail set on the forestay, and a mainsail abaft the mast. The sloop rig is very common in modern leisure sailing vessels. In older usage, a sloop may have more than one headsail, but with the jib (the outer headsail) also set on a stay. This differentiates from a cutter of the same era, where the jib would be set flying and a running bowsprit was used. Any bowsprit that might be fitted on a sloop was part of the standing rigging and remained in place at all times.
Sloop-of-war	1. In the 18th and 19th centuries, a small sailing warship carried 18 or fewer guns with a single continuous gundeck. 2. In the 18th and 19th centuries, any sailing warship bearing fewer than 20 guns.
Slop chest	A ship's store of merchandise, such as clothing, tobacco, etc., maintained aboard merchant ships for sale to the crew.
Slush	Greasy substance obtained by boiling or scraping the fat from empty salted meat storage barrels, or the floating fat residue after boiling the crew's meal. In the Royal Navy, it was a perquisite of the ship's cook, who could sell it or exchange it (usually for alcohol) with other members of the crew. Used for greasing parts of the running rigging of the ship and therefore valuable to the master and bosun.
Slush fund	The money obtained by the cook selling slush ashore. Used for the benefit of the crew (or the cook).
Smack	A traditional fishing boat used off the coast of England and the Atlantic coast of America for most of the 19th century and in small numbers up to the mid-20th century. Originally a cutter-rigged sailing boat, after about 1865 lengthened and given a ketch rig. Some had a topsail on the mizzen mast, others a bowsprit carrying a jib.
Small bower	The smaller of two anchors carried in the bow.
Smoking lamp	Restricted flame source lighted only during authorized smoking hours.[16]
Snag	2. An underwater obstruction on which equipment trailed from a vessel, such as fishing lines and nets, becomes caught, sometimes resulting in loss of the equipment.
Snagboat	A river boat resembling a barge with a superstructure for crew accommodations, equipped with deck-mounted cranes and hoists for removing snags and other obstructions from rivers and other shallow waterways.
Snatch block	A block with one cheek that is hinged, so that the bight of a rope can be inserted in the block (as opposed to threading the end of the rope into an ordinary block).
Snipe	1. Member of a ship's engineering department. 2. Mythical object of a "snipe hunt" for inexperienced crewmembers.
Snotter	A short rope, spliced together at the ends and covered with hide, that is seized to the mast to hold the lower end of a sprit.
Snotty	Royal Navy slang for a midshipman.
Snow	A form of brig where the gaff spanker or driver is rigged on a "snow mast", a lighter spar supported in chocks close behind the mainmast.
Snub	To quickly stop a line that is running out - usually by taking or tightening a turn on a bollard, cleat or winch drum.
Snug loaded	When all the cargo on a barge is stowed below in the hold and there is nothing on deck. In contrast to carrying a stack.
Society
Soft eye	An eye splice without a thimble fitted.
Sonar	(SOund NAvigation and Ranging) is used for many purposes. Passive sonars detect noise from marine objects, such as submarines, ships and marine animals. Active sonars emit a pulse of sound or “ping,” into the water and then listen for an echo when the signal is reflected off an object. To measure the distance to an object, one measures the time from emission of a pulse to reception. Some common sonar devices are: Side Scan Sonar —as the name implies, is a sonar that looks out sideways. It is used to map seafloor topography or to locate objects on the bottom or in the water column. It consists of a tow fish with a transducer running along each side. Acoustic pulses are transmitted orthogonal to the axis of the tow fish. The receiver measures the time it takes for the pulses to return and their strength. These are combined together to create a “shadow picture” that depicts the shape and texture of the seafloor and any objects laying on it. A good review of side scan sonars can be found at http://inventors.about.com/gi/dynamic/offsite.htm?site=http://www.instituteformarineacoustics.org/SonarPrimer/SideScanSonar.htm ... (more at Sonar)
Sou'wester	1. A storm originating from the southwest. 2. A type of waterproof hat with a wide brim over the neck, worn in storms.
Soul, souls	With a quantifier, can apply to the number of people on board ship; hence, SOS, “Save Our Souls”.
Sounding	Measuring the depth of the water. Traditionally done by "swinging the lead", now more commonly by echo sounding.
Spanker	A fore-and-aft or gaff-rigged sail on the aftmost mast of a square-rigged vessel and the main fore-and-aft sail (spanker sail) on the aftmost mast of a (partially) fore-and-aft rigged vessel such as a schooner, barque, or barquentine.
Spanker-mast	The aftmost mast of a fore-and-aft or gaff-rigged five-masted vessel such as a schooner or barquentine. A full-rigged ship has a spanker sail but not a spanker-mast (see jigger-mast).
Spar	A wooden (in later years also iron or steel) pole used to support various pieces of rigging and sails. The big five-masted full-rigged tall ship Preussen (German spelling: Preußen) had crossed 30 steel yards, but only one wooden spar – the little gaff of its spanker sail.
Spar torpedo	A weapon consisting of a bomb placed at the end of a long spar and attached to a boat.
Speaking tube	See communication tube.
Spencer	A trysail.
Spider band	Also spider hoop. An iron band around the base of a mast that holds a set of iron belaying pins.
Spindrift	Finely divided water swept from the crests of waves by strong winds. The presence of spindrift may be used to approximately estimate wind speed.
Spinnaker	1. A large sail flown in front of the vessel while heading downwind.[65] 2. A headsail set windward when running before the wind. The bargeman's spinnaker is his topmast staysail, tacked to the mast, and sheeted round the weather crosstree.
Spinnaker pole	A spar used to help control a spinnaker or other headsail.
Spirketting	The thicker planks of the ceiling, found at the bottom of the hold and continuing up the inside of the hull to the start of the quickwork (or lining).
Splice	To join lines (ropes, cables, etc.) by unraveling their ends and intertwining them to form a continuous line; to form an eye or a knot by splicing.
Splice the mainbrace	An order given aboard naval vessels to issue the crew with a drink, traditionally grog. The phrase "splice the mainbrace" is used idiomatically meaning to go ashore on liberty, intending to go out for an evening of drinking.
Splinter fleet	Also splinter navy. Informal term for wooden boats of various types the United States armed forces used during World War II. Some of the boats were civilian vessels brought into service for the war, while others were built during the war specifically for wartime service. Some were transferred to Allied countries.
Split lugsail	Two sails, foresail and mainsail on a lugsail yard, removing the need to dip the yard around the mast every time the vessel tacked.
Spoke
Sponson	A projection that extends outward (usually from the hull, but sometimes other parts of the vessel) to improve stability while floating, or to act as a securing point for other equipment. V
Sponsor	The person, traditionally a woman, who christens a ship at its launching ceremony.
Spotting top	A platform on a mast used to aid in gun laying.
Spreader	A spar on a sailboat used to deflect the shrouds to allow them to better support the mast.
Spring	A mooring warp that goes from the bow to a position on the quayside level with the stern (backspring) or led forward from the stern to a point level with the bow (forespring). A spring may be used in conjunction with the engine to swing the bow or stern away from a quayside to enable safe departure.
Springs	Big tides caused by the alignment of the Moon and Sun.
Sprit	A spar that supports a spritsail. It is attached to the mast near the deck and extends diagonally up to the peak of the sail. It is steadied by vangs.
Spritsail	1. A fore-and-aft sail, where the peak is supported by a sprit. It may be free-footed or use a boom. 2. A rig that uses a spritsail.
Sprittie	A spritsail-rigged barge.
Spurling pipe	A pipe that connects to the chain locker, from which the anchor chain emerges onto the deck at the bow of a ship.
Squadron	1. In general, any significant group of warships considered too small to be a fleet, but otherwise not strictly defined by size. In some navies, the term flotilla may be used instead of or in addition to squadron.
Square	To place at right angles with the mast or keel and parallel to the horizon, e.g. "to square the yards".
Square meal	A sufficient quantity of food. Meals on board ship were served to the crew on a square wooden plate in harbor or at sea in good weather. Food in the Royal Navy was invariably better or at least in greater quantity than that available to the average landsman. However, while square wooden plates were indeed used on board ships, there is no established link between them and this particular term. The OED gives the earliest reference from the US in the mid-19th century.
Square rig	A generic type of sail and rigging arrangement in which the primary driving sails are carried on yards that are perpendicular, or "square", to the keel of the vessel and to the masts. A ship mainly so rigged is said to be square-rigged.
Square rigger	A square-rigged ship.
Squared away	Yards held rigidly perpendicular to their masts and parallel to the deck. This was rarely the best trim of the yards for efficiency but made a pretty sight for inspections and in harbor. The term is applied to situations and to people figuratively to mean that all difficulties have been resolved or that the person is performing well and is mentally and physically prepared.
Squat effect	The phenomenon by which a vessel moving quickly through shallow water creates an area of lowered pressure under its keel that reduces the ship's buoyancy, particularly at the bow. The reduced buoyancy causes the ship to "squat" lower in the water than would ordinarily be expected, and thus its effective draught is increased.
Squid	A derogatory term for a US Navy sailor.
Stability	Any seagoing vessel has the constant need for hydrostatic stability. A naval architect , like an airplane designer, is concerned with stability . What makes the naval architect’s job unique is that a ship operates in two fluids simultaneously: water and air. Even after a ship has been designed and put to sea, marine engineers face the challenge of balancing cargo, as stacking containers vertically increases the mass of the ship and shifts the center of gravity higher. The weight of fuel also presents a problem, as the pitch of the ship may cause the liquid to shift, resulting in an imbalance. In some vessels, this offset will be counteracted by storing water inside larger ballast tanks. Marine engineers are responsible for the task of balancing and tracking the fuel and ballast water of a ship. ... (more at Stability)
Stack	Also funnel. 1. Another name for a funnel.
Stack marking	A logo or other type of livery on a ship′s stack indicating which private entity, such as a shipping line, or government agency owns or operates her. Generally, all the ships belonging to the fleet of a single company or agency will have the same stack marking.
Stackie	A barge designed to take a large deck cargo, usually of hay or straw needed to feed working horses.
Stanchion	A vertical post near the edge of a deck that supports life-lines; a timber fitted in between the frame heads on a wooden hull or a bracket on a steel vessel, approx one meter high, to support the bulwark plank or plating and the rail.
Stand	(of a ship or its captain) To steer, sail, or steam, usually used in conjunction with a specified direction or destination, e.g. "The ship stood out of the harbor" or "The ship stood toward the east" or "The ship stood toward the missing vessel's last known position".
Stand-on (vessel)	A vessel directed to keep her course and speed where two vessels are approaching one another so as to involve a risk of collision.
Standing part	The section of a rope at a cleat or a block that is under tension, as opposed to the loose end.
Standing rigging	Rigging that supports masts and spars and is not manipulated during normal operations. Contrast running rigging.
Stanliff	A heavy wire cable attached to the mast at the hounds to support the weight of a spritsail at the heel.
Starboard	The right side of a ship or boat; towards the right-hand side of a vessel facing forward (toward the bow). Denoted with a green light at night. Derived from the old steering oar or "steerboard", which preceded the invention of the rudder.
Starboard tack	When sailing with the wind coming from the starboard side of the vessel. Vessels on starboard tack generally have right-of-way over vessels on port tack.
Starter	A rope used as a punitive device. See teazer and togey.
Stateroom	1. A superior cabin for a vessel's officer. 2. In American usage, a private passenger cabin on a transport or cruise ship.
Station	2. In Newfoundland, a harbor or cove with a foreshore suitable for a facility to support nearby fishing.
Station ship	A ship assigned to a particular station, such as a port or a geographic area, usually to support naval vessels and operations. A station ship may patrol the local area, or provide personnel to other ships, or provide fuel or services such as repairs.
Stay	1. A strong rope supporting a mast and leading from the head of one mast down to some other mast or other part of the vessel; any rigging running fore (forestay) and aft (backstay) from a mast to the hull. The stays support a mast's weight forward and aft, while the shrouds support its weight from side to side. 2. To incline forward, aft, or to one side by means of stays, e.g. to "stay a mast".
Stayfall	A flexible wire cable rove through blocks, one on the stemhead and one on the end of the forestay. This is the means by which the mainmast is lowered.
Staysail	A sail whose luff is attached to a stay. If set on the most forward (or only) mast, a staysail is a headsail. Where more than one headsail is set, the staysail is generally the one closest to the mast.
Steamer	Also steamboat or steamship. A vessel equipped with steam propulsion.
Steerage	1. The effect of the helm on a vessel; the act of steering a vessel. 2. A 19th- and early 20th-century term for the section of a passenger ship that provided inexpensive accommodation with no individual cabins.
Steerageway	The minimum speed at which a vessel answers the helm, below which she cannot be steered. Speed sufficient for the rudder to "bite".
Steering flat	The compartment on a vessel that contains the steering gear.
Steering oar	Also steering board. A long, flat board or oar that went from the stern to well underwater, used to steer vessels before the invention of the rudder. Traditionally on the starboard side of a ship (the "steering board" side).
Steersman	Another name for a helmsman.
Steeve	1. A spar or derrick with a block at one end, used for stowing cargo. 2. To incline upwards at an angle (used especially of a bowsprit) rather than lie horizontally; to set at a particular upwards incline.
Stem	1. An extension of the keel at the forward end of a ship. 2. On a barge, the foremost timber set vertically to the keel, forming the head of the stem; it carries the forestay and other rigging.
Stern	The rear part of a ship, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. Contrast bow.
Stern chaser	See chase gun.
Stern tube	1. The tube under the hull bearing the tailshaft for propulsion (usually at the stern). 2. A torpedo tube mounted in the stern of a submarine.
Sterncastle	Another name for an aftercastle.
Sterndrive	Stern drive. Also: Z-drive A propeller drive system similar to the lower part of an outboard motor extending below the hull of a larger power boat or yacht, but driven by an engine mounted within the hull. Unlike a fixed propeller (but like an outboard), the boat may be steered by twisting the drive. See also inboard motor.
Sternender	Great Lakes slang for a vessel which has all of her cabins aft.
Sternlight	A white running light displayed on the stern of a vessel.
Sternpicker	A gillnetter that fishes by deploying a gillnet from the stern.
Sternpost	The upright structural member (or post) at the stern of a (usually wooden) ship or boat, to which are attached the transoms and the rearmost corner part of the stern. It rests on ("fays to") the ship's keel, and may be vertical or tilted ("raked") slightly aft.
Sternsheets	1. The area at the stern of an open boat. 2. The benches at the stern of an open boat that forms the or seating in the stern.
Sternwalk	An external walkway or gallery for the use of officers installed on the stern, chiefly of British warships until the early 20th century.
Sternway	The reverse movement of a boat or watercraft through the water.
Sternwheel	1. A stern-mounted paddle wheel used for propulsion by a paddle steamer. 2. Propelled by a sternwheel (e.g. a "sternwheel steamer").
Sternwheeler	A paddle steamer propelled by a sternwheel.
Steward	A member of a vessel's crew involved in commissary duties or in personal services to passengers or other crew members.
Stiffeners	All plates in the hull structure need to be strengthened in various ways to increase their load-absorbing capabilities. For the same reason, stiffening members of multiple types are placed in all directions (transverse and longitudinal). These strength members are standard rolled steel sections or simply plates and bars, depending on the requirement.
Stocks	The frame that supports a ship or boat when it is being built.
Stoker	See fireman.
Stone Fleet	A fleet of old ships loaded with stone, sand, or dirt and scuttled by the United States Navy during the American Civil War to block ports of the Confederate States of America in 1861 and 1862.
Stone frigate	Informal Royal Navy term for a naval shore establishment.
Stood	See stand.
Stopper knot	A knot tied in the end of a rope, usually to stop it passing through a hole; most commonly a figure-eight knot.
Stoppers	A short rope to check a cable in a fixed position. Anchor stoppers hold the anchor when catted, bitt stoppers and deck stoppers are used to retain the cable when at anchor, shroud stoppers contain a damaged shroud, and foretack and sheet stoppers secure the tacks until they are belayed.
Storeship	Also store ship or stores ship. 1. During the Age of Sail and immediately afterwards, a captured ship used to stow supplies and other goods for naval purposes.
Stove	Also stove in. (past tense of stave, often applied as present tense) To smash inward; to force a hole or break in, as in a cask, door, ship's hull, or other (wooden) barrier.
Stow	To store or put away, e.g. personal effects, tackle, or cargo.
Stowage	The amount of room for storing materials on board a ship.
Stowaway	A trespasser on a ship; a person aboard a ship without permission and/or without payment, who usually boards undetected, remains hidden aboard, and jumps ship just before making port or reaching a port's dock; sometimes found aboard and imprisoned in the brig until the ship makes port and the prisoner can be transferred to the custody of police or military.
Straggler	In a convoy, a ship that is unable to maintain speed and falls behind.
Straight decker	1. Originally, a ship built with her pilothouse forward and engines aft to provide a continuous hold in between, a design commonly associated with ships which operate on the Great Lakes in North America. 2. In more recent usage, a Great Lakes bulk carrier which lacks self-unloading machinery.
Straits, Channels And Canals	Strait is a narrow water-body interconnecting two much larger water bodies (Eg. Singapore and Malacca Straits connect the Bay of Bengal and the South China Sea). Water flow is in both directions and is tidal. Most importantly, straits are naturally formed without human intervention. ... (more at Straits, Channels And Canals)
Strake	A continuous line of planking on a wooden hull going from bow to stern. Successive strakes, one above the other, form the outer skin of a hull. In a steel hull the same term can be applied to a continuous line of steel plates all fastened at the same level.
Strakes	A continuous band of hull planking or plates on a ship (also means the width of the bands)
Strakes	Strakes are plates in the side and bottom structure. The A strake or the Garboard strake are the plates on either side immediately adjacent to the keel. The immediate plates on either side are referred to as strakes B, C, D, and so on. The strake plates at the bottom corners or the turn of the bilge are known as the bilge strakes. Similarly, the outer uppermost side vertical plating at the deck edge is known as sheer strakes.
Stretcher	An inclined foot rest attached to the boat, to which a rower may place and in some instances (usually in competition) attach his feet.
Strike	1. To haul down or lower (a flag, mast, etc.). 2. To surrender the vessel to the enemy, from "strike the colors".
Strike the colors	To surrender the vessel to an enemy, from the custom during the Age of Sail of lowering the vessel's ensign to indicate that she is surrendering.
Stringer
Stringers	The longitudinals placed at the vessel’s side shell platings are called stringers. For double hull configurations, stringers are both for the inner and outer shell.
Studding sails	(pronounced /ˈstʌnsəl/) Long and narrow sails, used in lighter winds, on the outside of the large square sails.
Stumpy	1. A spritsail barge without a topmast. Normal form before 1850, the stumpies sprit was longer than those used in topsail barges, as the mainsail was cut with a higher peak. 2. A tops'l barge underway without her topsails set.
Sub-Bottom Profilers	use low-frequency sonar (2 to12kHz) to penetrate the seafloor. Sound pulses are reflected from the boundaries between sediment layers. This information can be used for geological studies and to find buried objects such as shipwrecks, mines and lost equipment. In side scan sonar surveying, it is desirable to cover the seabed quicker and at higher resolutions. This causes great difficulty for conventional side scan technology. There are only two choices—using higher frequencies (to achieve narrower beams and thus higher resolutions) or using longer apertures to achieve the same effect. The downside to this approach is either shorter operational ranges with higher frequencies (compromising coverage rates) or problems associated with handling large tow fish. Similarly, as the imagery is tied to the sonar beam width, the resolution of conventional side scan degrades with range. Two techniques have been developed to get around these obstacles. Multi-beam side scan sonars use several transducers along each side of the tow fish. With beam steering and focusing techniques, several simultaneous adjacent parallel beams are generated per side. This allows for 100 % coverage at very high tow speeds with extraordinary resolution and image clarity. Another method, Synthetic Aperture Sonar (SAS) synthesises a long aperture image by adding successive sonar returns, which are processed to compensate for the movement between returns and other factors. The results are much improved resolutions.
Sub-feeder Panels
Subchaser	See submarine chaser.
Submarine	1. Generally, a watercraft capable of independent operations underwater, able to renew its own power and breathing air. A submarine differs from a submersible, which has more limited underwater capabilities. By naval tradition, any submarine is referred to informally as a "boat" regardless of its size. 2. Most commonly, a large, crewed vessel capable of independent underwater operations.
Submarine chaser	Also subchaser. A small naval vessel designed for antisubmarine warfare, introduced during World War I and obsolete by the late 20th century.
Submarine tender	A naval auxiliary ship designed to supply submarines and support their operations. Known in British English as a submarine depot ship.
Submersible	A small watercraft capable of operating underwater but which requires the support of a surface vessel, a surface platform, a shore team, or a larger undersea vessel such as a submarine. A submersible contrasts with a submarine in that a submarine is capable of fully autonomous operations, including generation of its own power and breathing air. However, colloquially, the term "submarine" often indiscriminately refers to any vessel capable of underwater operations, including those that technically are submersibles.
Submersibles	: Manned submersibles are noncombatant craft capable of independent operation on and under the water’s surface. Manned submersibles have their own propulsion power and a means for direct viewing for the occupants who are in a dry one-atmosphere cabin. Manned submersibles have a long history going back hundreds of years and now employ many of the technologies described in this glossary. Today they are primarily used forscientific research, exploration and tourism Major subsystems include the pressure hull, viewing ports, life support systems, exostructure, ballast/trim, propulsion, batteries and fairings/sail. Operational instrumentation typically includes lights, cameras , sonar , thruwater communications, and often a manipulator. Navigation equipment consists of a pressure sensor, tilt sensor, gyrocompass , doppler velocity log (DVL), underwater tracking system, altimeter and perhaps an inertial navigation system that would integrate the data from all the other sensors. In addition, missionspecific scientific equipment is often added. The MTS Manned Submersibles Committee web site at http://www.mtsociety.org/pro_committees/mannedsubmersibles/default.html has a suggested reading list and links to many valuable resources. Also, the out-of-print classic “Manned Submersibles” by Frank Busby is available on-line at http://busby.psubs.org/html/page-001.html . A comprehensive compilation of American subs by Will Forman is The History of American Deep Submersible Operations .
Sunfish	A personal-sized, beach-launched sailing dinghy with a pontoon-type hull, daggerboard, and lateen sail mounted to an un-stayed mast.
Supercargo	A person aboard a vessel who is employed by the cargo owner. Duties include selling merchandise in ports, as well as buying and receiving goods for the return voyage.
Superfiring
Superstructure	The parts of a ship or boat, including a sailboat, fishing boat, passenger ship, or submarine, that project above her main deck. This does not usually include its masts or any armament turrets.
Surface-Supplied Air Diving	: Divers tethered to a surface-supplied-air-diving system can achieve dives up to 190 feet of seawater (FSW) in air diving and 300 FSW in mixed gas diving. Air is supplied via an air compressor or high-pressure air flasks. A surface-supplied-air diving system can permit a diver to stay down for a longer period of time than a SCUBA system would allow.
Surfboat
Survey vessel	Any type of ship or boat that is used for mapping a body of water's bottom, benthic zone, full water column, and surface for purposes of hydrography, general oceanography, marine salvage, dredging, marine archaeology, or the study of marine habitats.
Surveyor	An individual with specific technical knowledge acting on behalf of the Society in performing the Services.
Swallow	The gap in the shell of a block through which a line passes over a sheave.
Swatchway	A twisting channel navigable by shallow vessels at high water, generally found between sandbanks (e.g. in the Thames Estuary) or between a sandbank and the shore.
Sway	1. A vessel's lateral motion from side to side. 2. (v.) To hoist, e.g. "sway up my dunnage".
Sweat	A technique to finally tension a halyard, by pulling alternatively on the tail from the cleat and at right angles on the taut standing line.
Sweep	1. A long oar used to row, steer, or maneuver an unpowered lighter or sailing vessel when there is no wind. 2. Rowing: A rower who rows with a single oar and primarily on only one side of a boat.
Swept	Cleared of dangers such as naval mines and obstructions, e.g., "The swept channel was safe for vessels to use."
Swig
Swimhead	Swim-head. Swim-headed Having a straight overhanging bow and stern.
Swimmie	Also muffie. A barge with a square overhanging bow, such as a swimhead lighter.
Swinging Circle And Turning Circle	Swinging and Turning Circles – ship terms related to vessel navigation are often confused. ... (more at Swinging Circle And Turning Circle)
Swinging the compass	Measuring the accuracy in a ship's magnetic compass so its readings can be adjusted, often accomplished by turning the ship and taking bearings on reference points. Essentially synonymous with "swinging the ship".
Swinging the lamp	Telling sea stories. Refers to lamps slung from the deckhead that swing while at sea, and often used to describe a storyteller who is exaggerating.
Swinging the lead	1. Measuring the depth of water beneath a ship using a lead-weighted sounding line. Regarded as a relatively easy job. 2. Feigning illness, etc., in order to avoid a difficult job.
Swinging the ship	Turning the ship and steadying her on various headings while taking bearings on reference points to measure the accuracy of her magnetic compass. Essentially synonymous with "swinging the compass".
Switchboards
T.E.V. (or TEV)	A prefix for "turbo-electric vessel", used before a ship's name.
TAS	Towed Array Sonar
Tabernacle	Also mast case. A large bracket attached firmly to the deck, to which the foot of the mast is fixed. It has two sides or cheeks and a bolt forming the pivot around which the mast is raised and lowered.
Tack	1. A leg of the route of a sailing vessel, particularly in relation to tacking and to starboard tack and port tack. 2. Another name for hardtack.
Tacking	1. A sailing maneuver by which a sailing vessel whose desired course is into the wind (i.e. in the opposite direction from which the wind is blowing) turns its bow toward and through the wind, such that the direction from which the wind fills the sails changes from one side of the boat to the other, thereby allowing progress in the desired direction. A series of tacking moves, effectively "zig-zagging" back and forth across the wind, is called beating, and allows the vessel to sail directly upwind, which would otherwise be impossible.[74] 2. Another name for going about.
Tacking duels	In sailboat racing, on an upwind leg of the race course, the complex maneuvers of lead and overtaking boats to vie for the aerodynamic advantage of clear air. This results from the ongoing strategy of the lead boat's effort to keep the following boat(s) in the blanket of disturbed bad air he is creating.
Tackle	A pair of blocks through which is rove a rope to provide an advantageous purchase. Used for lifting heavy loads and to raise and trim sails.
Tactical diameter	The perpendicular distance between a ship's course when the helm is put hard over and her course when she has turned through 180 degrees; the ratio of the tactical diameter divided by the ship's length between perpendiculars gives a dimensionless parameter that can be used to compare the maneuverability of ships.
Taffrail	A rail at the stern of a boat that covers the head of the counter timbers.
Tail	The loose end of a rope that has been secured to a winch or a cleat.
Tailshaft	A kind of metallic shafting (a rod of metal) to hold the propeller and connected to the power engine. When the tailshaft is moved, the propeller may also be moved for propulsion.
Taken aback	An inattentive helmsman might allow the dangerous situation to arise where the wind is blowing into the sails "backwards", causing a sudden (and possibly dangerous) shift in the position of the sails.
Taking on water	Also taking water and taking in water. Said of a vessel, to fill with water slowly, either because of a leak or because of waves washing across the deck. The term can be used to describe water entering the vessel by waves washing over her bow or stern, e.g., "The freighter took water over her bow," or "The motorboat took water over her stern." A vessel which continues to take on water eventually will sink.
Taking the wind out of his sails	To sail in a way that steals the wind from another ship. Compare overbear.
Tall ship	A large, traditionally-rigged sailing vessel.
Tally	The operation of hauling aft the sheets, or drawing them in the direction of the ship's stern.
Tanker	Also tank ship or tankship. A ship designed to transport liquids in bulk.
Target ship	A vessel, typically an obsolete or captured warship, used for naval gunnery practice or for weapons testing. The term includes both ships intended to be sunk and ships intended to survive and see repeated use as targets.
Tartane	Also tartan. A small, lateen-rigged, single-masted sailing ship used in the Mediterranean for fishing and coastal trade from the 16th century to the late 19th century.
Task Force
Tattle tale	Light cord attached to a mooring line at two points a few inches apart with a slack section in between (resembling an inchworm) to indicate when the line is stretching from the ship's rising with the tide. Obviously only used when moored to a fixed dock or pier and only on watches with a flood tide.
Tell-tale	Also tell-tail. A light piece of string, yarn, rope, or plastic (often magnetic audio tape) attached to a stay or a shroud to indicate the local wind direction. They may also be attached to the surface and/or the leech of a sail to indicate the state of the air flow over the surface of the sail. They are referenced when optimizing the trim of the sails to achieve the best boat speed in the prevailing wind conditions. See dogvane.
Tender	Also ship's tender. 1. A type of naval auxiliary ship designed to provide advanced basing services in undeveloped harbors to seaplanes, flying boats, torpedo boats, destroyers, or submarines.
Texas	A structure or section of a steamboat that includes the pilothouse and the crew's quarters, located on the hurricane deck, in this case also called the texas deck.
Texas deck	Also hurricane deck. The deck of a steamboat on which its Texas is located.
Thickness Measurement	T-min, T-Rule….
Thimble	A round or heart-shaped grooved ring of iron inserted into an eye-splice.
Third mate	Also third officer. A licensed member of the deck department of a merchant ship, typically fourth, or on some ocean liners fifth, in command; a watchkeeping officer, customarily also the ship's safety officer, responsible for the ship's firefighting equipment, lifeboats, and other emergency systems. Other duties of the third mate vary depending on the type of ship, its crewing, and other factors.
Third officer	See third mate.
Thole pin	A vertical wooden peg or pin inserted through the gunwale to form a fulcrum for oars when rowing. Often used in pairs to create a gap in which the oar is placed, but used singly if the oar has a thickened section pierced with a hole which takes the thole pin. See also rowlock.
Three sheets to the wind	On a three-masted ship, having the sheets of the three lower courses loose will result in the ship meandering aimlessly downwind. Also used to describe a sailor who has drunk strong spirits beyond his capacity.
Throat	1. The forward top corner of a square fore-and-aft sail. 2. The end of the gaff, next to the mast.
Thunderboat	Alternative term for a hydroplane.
Thwart	Pronounced /θwɔːrt/. A bench seat across the width of an open boat.
Tide Gauges	are used to measure changes in sea level. This is important to know for many reasons, including the correction echo sounder data used in making hydrographic charts. The first known tide measuring devices were used by the Egyptians 5,000 years ago, making tide gauges the first known marine technology. Wooden or reed sticks and later marble columns planted in the river bottom were sufficiently long enough to extend above the waterline where the fluctuating level of the Nile River could be measured against markings. The hydrological information collected is one the longest scientific time-series data sets ever collected. Today, tide staffs are still widely used. ... (more at Tide Gauges)
Tier	Vessels moored alongside each other offshore.
Tiller	A lever used for steering, attached to the top of the rudder stock. Used mainly on smaller vessels, such as dinghies and rowing boats.
Tilt boat	A square sail ferry operating out of Gravesend. Not less than 15 tons, carrying no more than 37 passengers, it had 5 oarsmen afore the mast.
Timber drogher	Another name for a disposable ship.
Timber ship	Another name for a disposable ship.
Timoneer	A name given, on particular occasions, to the steersman of a ship. From the French timonnier.
Tingle	A thin temporary patch.
Toe the line	Also toe the mark. At parade, sailors and soldiers were required to stand in line, their toes in line with a seam of the deck.
Toe-rail	A low strip running around the edge of the deck like a low bulwark. It may be shortened or have gaps in it to allow water to flow off the deck.
Tompion	Also tampion. A block of wood inserted into the barrel of a gun on a 19th-century warship to keep out the sea spray; also used for covers for the ends of the barrels of the guns on more modern ships, the larger of which are often adorned with the ship's crest or other decoration.
Tonnage	1. Any of various measures of the size or cargo-carrying capacity of a ship in terms of weight or volume. 2. Builder's Old Measurement, also tons burden: a volumetric measurement of cubic capacity used to calculate the cargo capacity of a ship, used in England and later the United Kingdom, from approximately 1650 to 1849 and in the United States from 1789 to 1864. It estimated the tonnage of a vessel based on her length and maximum beam. The British formula yielded a slightly higher value than the U.S. formula.
Top	The platform at the upper end of each (lower) mast of a square-rigged ship, typically one-fourth to one-third of the way up the mast. The main purpose of a top is to anchor the shrouds of the topmast that extend above it. See also fighting top.
Topgallant	The mast or sails above the tops. See topgallant mast and topgallant sail.
Tophamper	1. A collective term for the masts, yards, sails, and rigging of a sailing ship, or for similarly insubstantial structures above the upper deck of any ship. 2. Unnecessary spars and rigging kept aloft on a vessel′s masts.
Topman	A crewmember stationed in a top.
Topmast	The second section of the mast above the deck; formerly the upper mast, later surmounted by the topgallant mast; carrying the topsails.
Topmast pole	Part of the spar between the hounds and the truck.
Topping lift	A line that is part of the rigging on a sailing boat; it applies upward force on a spar or boom. The most common topping lift on a modern sailing boat is attached to the boom.
Topsail	The second sail (counting from the bottom) up a mast. These may be either square sails or fore-and-aft ones, in which case they often "fill in" between the mast and the gaff of the sail below.
Topsides	The part of the hull between the waterline and the deck. See also above-water hull.
Torpedo	1. Prior to about 1900, the term for a variety of explosive devices designed for use in water, including mines, spar torpedoes, and, after the mid-19th century, "automotive", "automobile", "locomotive", or "fish" torpedoes (self-propelled weapons which fit the modern definition of torpedo). 2. Since about 1900, a term used exclusively for a self-propelled weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with its target or in proximity to it.
Torpedo boat	A small, fast, cheap naval vessel of the latter part of the 19th century and first half of the 20th century designed to carry torpedoes into combat, thus threatening much larger warships. Replaced during the second half of the 20th century by the fast attack craft.
Torpedo net
Touch and go	1. The bottom of the ship touching the bottom, but not grounding. 2. Stopping at a dock or pier for a very short time without tying up, to let off or take on crew or goods.
Towed Vehicles	: Many types of underwater towed vehicles have been developed for oceanographic real-time surveys. They offer the capability of moving in wide area with stable attitude at speeds much faster then ROVs and AUVs . Towed vehicles are used for such tasks as monitoring the oceanographic environment, surveying the seabed and inspecting pipelines on the seabed. Some types can be steered and others can be winched in and out.
Towing	The operation of drawing a vessel forward by means of long lines.
Traffic separation scheme	Shipping corridors marked by buoys that separate incoming from outgoing vessels. Sometimes improperly called sea lanes.
Trailboard	A decorative board at the bow of a vessel, sometimes bearing the vessel's name.
Training ship	A ship used to train students as sailors, especially a ship employed by a navy or coast guard to train future officers. The term refers both to ships used for training at sea and to old, immobile hulks used to house classrooms.
Tramp freighter	A cargo ship engaged in the tramp trade.
Tramp steamer	A steamship engaged in the tramp trade.
Tramp trade	The shipping trade on the spot market in which the vessels involved do not have a fixed schedule or itinerary or published ports of call. This contrasts with freight liner service, in which vessels make regular, scheduled runs between published ports.
Tramper	Any vessel engaged in the tramp trade.
Transmitting station	British term for a room located in the interior of a ship containing computers and other specialized equipment needed to calculate the range and bearing of a target from information gathered by the ship's spotters and range finders. These were designated "plotting rooms" by the United States Navy.
Transom	1. A lateral member fastened inside the sternpost, to which the hull and deckplanks are fitted. 2. The aft "wall" of the stern; often the part to which an outboard unit or the drive portion of a sterndrive is attached.
Transom stern	A stern which ends in a vertical "wall," or transom, a flat area that extends from the waterline or a point above the waterline up to the deck.
Transport	See troopship.
Transverse
Transverse Section Modulus
Transverse and Longitudinal Framing	For shorter vessels, there are more transverse members like frames than longitudinals, which are comparatively closely spaced. This is due to the effects of lateral loading, and this system is known as transverse framing. Longer vessels are more susceptible to flexural or longitudinal loading effects, and hence they have closely spaced longitudinal members greater than transverse, and this system is known as longitudinal framing.
Travelers	1. Small fittings that slide on a track, rod, or line. The most common use is for the inboard end of the mainsheet. 2. A more esoteric form of traveler consists of "slight iron rings, encircling the backstays, which are used for hoisting the top-gallant yards, and confining them to the backstays".[78]
Trawler	1. Commercial trawler: a fishing boat that uses a trawl net or dragnet to catch fish. 2. A fisherman who uses a trawl net.
Treenail	Also trenail, trennel, or trunnel. A wooden peg, pin, or dowel used to fasten pieces of wood together, such as the hull, gunwales, thwarts, etc.
Trial trip	A (usually short) voyage for a new ship to test its capabilities and ensure that everything is functioning correctly. A new ship will usually have one or more trial trips before embarking on its maiden voyage.
Triangular trade	A historical term for a pattern of trade among three ports or regions in which each port or region imports goods from one of the other two ports or regions in which there is no market for its exports, thus rectifying trade imbalances between the three ports or regions as well as allowing vessels to take the best advantage of prevailing winds and currents along the three trade routes. The best known example is the Atlantic triangular trade pattern of the late 16th through the early 19th centuries, in which vessels carried finished goods from northeastern North America or Europe to Africa, slaves from Africa to the Americas, and cash crops and raw materials from the Americas to either northeastern North America or Europe.
Trice	To lift up something by means of a rope running through a block set above it, to get it out of the way. Most commonly used in tricing up the tack of a loose-footed gaff sai to reduce sail area and (sometimes) to give better visibility to the helmsman.
Trick	A period of time spent at the wheel, e.g. "my trick's over".
Trim	1. The relationship of a ship's hull to the waterline. 2. Adjustments made to sails to maximize their efficiency.
Trimaran	A vessel with three hulls.
Trimmer	Sometimes coal trimmer. A person responsible for ensuring that a vessel remains "in trim" (that the cargo and fuel are evenly balanced). An important task on a coal-fired vessel, as it could get "out of trim" as coal is consumed.
Tripod mast
Tripping line	A buoyed line attached to the crown of an anchor to facilitate breaking it out.
Troller	A fishing vessel rigged to fish by trolling.
Trooping	Operating as a troopship.
Troopship
Truck	2. A temporary or emergency place for a lookout.
True bearing	An absolute bearing using true north.
True north	The direction of the geographical North Pole.
Truncated counter	A counter stern that has been truncated to provide a kind of transom. It may have windows, serving a large aft stateroom. Popular on larger cruising yachts.
Truss	The rope or iron used to keep the center of a yard to the mast.
Trysail	Also spencer. A small, strong, fore-and-aft sail set abaft (behind) the mainmast or other mast of a sailing vessel in heavy weather.
Tugboat	Also tug. A boat that manoeuvers other vessels by pushing or towing them. Tugs are powerful for their size and strongly built, and some are ocean-going.
Tumblehome	A hull shape, when viewed in a transverse section, in which the widest part of the hull is someway below deck level.
Tuna clipper	A fishing boat based on the United States West Coast and used for commercial tuna fishing. A typical tuna clipper is diesel-powered, has her deckhouse forward and her bait tanks aft, and is outfitted with iron racks around her stem from which her crew uses heavy bamboo poles to fish for tuna.
Turbines
Turn	A knot passing behind or around an object.
Turn To (Turn Two)	A term meaning "get to work", often hand-signed by two fingers and a hand motion in turning fashion.
Turnbuckle	See bottlescrew.
Turret	2. Since the late 19th century, an enclosed, armored, rotating gunhouse mounted above a barbette, with the gun(s) and their rotating turntable mounted in the barbette protected by the gunhouse; in 20th- and 21st-century usage, this generally is any armored, rotating gun installation on a warship.
Turtleback deck	A weather deck that has a distinct convex rounded over shape, similar to the back of a turtle. Used on ships of the whaleback type and on the forward weather deck of torpedo boats."
Turtling	In dinghy sailing especially (but also in other boats), a boat is said to be "turtling" or to "turn turtle" when the boat is fully inverted with the mast pointing near vertically downwards, but may remain floating.
Tweendeck	A deck on a general cargo ship located between the main deck (or weather deck) and the hold space. A general cargo ship may have one or two tweendecks (or none at all).
Tweendeck space	The space on a tweendeck available for carrying cargo or other uses.
Tweendecker	A general cargo ship equipped with one or more tweendecks.
Two blocks	When the two blocks in a tackle have become so close that no further movement is possible as in chock-a-block.
Two six heave	A command used to coordinate a group of people pulling on a rope. Originally a sailing navy term referring to the two members of a gun crew (numbers two and six) who ran out the gun by pulling on the ropes that secured it in place.
Tye	A chain or rope used for hoisting or lowering a yard. A tye runs from the horizontal center of a given yard to a corresponding mast and from there down to a tackle. Sometimes more specifically called a chain tye or a rope tye.
U.N.P.O.C.	An abbreviation for "Unable to navigate, probably on course"; a 19th-century term used in log books of vessels left without accurate navigational guidance due to poor visibility and/or proximity to the North Pole (where magnetic compasses are difficult or impossible to use). Dropped out of common usage in the 1950s with improvements in maritime navigational aids.
Unassisted sailing	Any sailing voyage, usually single-handed, with no intermediate stops or physical assistance from external sources.
Under the weather	Serving a watch on the weather side of the ship, exposed to wind and spray.
Underwater Acoustic Imaging	is used to produce high-quality images in water where visibility is too poor to use optical methods. In underwater acoustic imaging, electrical energy (electricity) is sent to a crystal, which causes the crystal to vibrate. The sound of the vibration (mechanical energy) travels out into the water column until it hits an object and is reflected back to the crystal. After the energy returns to the crystal, a computer converts it to an image.
Underwater Positioning and Tracking Systems	are used to identify the location of an object or vehicle underwater. Since radios do not transmit through water, GPS cannot be used unless an antenna is cabled to the surface. Several acoustic methods have been developed for the purpose of underwater navigation. These include: Long Base Line (LBL) uses several transponders on the seafloor. The distance between each transponder is measured. A transducer on the vessel, ROV , AUV or tow fish, interrogates each transponder and the ranges to each are measured. From this= information, the position of the subsea platform can be determined by triangulation. ... (more at Underwater Positioning and Tracking Systems)
Underwater hull	Also underwater ship. The underwater section of a vessel beneath the waterline, normally not visible except when in drydock or, historically, when careened.
Underway	Also under way. (of a vessel) At sea; i.e. not at anchor, made fast to the shore, or aground. This definition has legal importance in the International Regulations for Preventing Collisions at Sea.
Underway replenishment	A method employed by navies to transfer fuel, munitions, and stores from one ship to another while underway. Sometimes abbreviated as UNREP.
Unit	means a vessel of any of several types, including stationary floating platforms, semi-submersible and even mobile units equipped with propulsion drives.
Unreeve	To pull a rope from a sheave or block.
Unship	1. To remove from a vessel. 2. To remove an oar or mast from its normal position.
Up-and-down	The description given to the position of the anchor chain, usually used when the anchor is being raised and indicating that the chain has been hauled in tightly such that the vessel is floating directly above the anchor, which is just about to be broken out of the ground. Used more rarely to refer to a situation where the anchor chain is slack and hangs vertically down from the hawsepipe.
Up-behind	An order to slack off quickly and run slack to a belaying point. This order is given when a line or wire has been stopped off or falls have been four-in-hand and the hauling part is to be belayed.
Upbound	1. Traveling upstream, against the current. 2. In the Great Lakes region, traveling westward (terminology used by the Saint Lawrence Seaway Development Corporation).
Upper-yardmen	Specially selected personnel destined for high office.
Uppers	Also peaks. The brails above the mains.
V-hull	The shape of a boat or ship in which the sections of the hull bottom slope downward in a straight line to the keel.
VCS	Vapor Control System
Vang	1. A line leading from the gaff to either side of the deck, used to prevent the gaff from sagging. 2. One of a pair of ropes leading from the deck to the head of a spritsail. It steadies the sprit and can be used to control the sail's performance during a tack. The vang fall blocks are mounted slightly afore the main horse while rolling vangs are extra preventers which lead forward to keep the sail to leeward in heavy weather.
Vanishing angle	The maximum degree of heel after which a vessel becomes unable to return to an upright position.
Vedette	Also vedette boat. A small naval patrol boat used for scouting enemy forces.
Veer Away	To let go a rope gently.
Vertical replenishment	A method of supply of seaborne vessels by helicopter. Abbreviated VERTREP.
Very good
Very well
Vessel	Ships, boats, craft and other special units, as for example offshore structures, floating units and underwater craft.
Viol	Also voyl. A large rope used to unmoor or heave up the anchor.
Voice pipe	Also voice tube. See communication tube.
Voyage	1. A long journey by ship. 2. To go on such a journey.
Voyl	See viol.
Waft	Another name for a signal flag.
Waits clothes	Also armings or fights. Colored cloths or sheets hung around the outside of a ship's upper works, both fore and aft, and before the cubbridge heads, used as an adornment during ceremonious occasions and as a visual screen during times of action in order to protect the men aboard.
Wake	Turbulence in the water behind a moving vessel. Not to be confused with wash.
Walch Crane Rig (WCR)	Abbreviated as WCR (Pronounced “Wicker”), this is a mobile combined systems construction, repair and refit vessel that provides services to all forms of seasteading habitats. Visible from a distance due to its sheer size and mass, its cranes are able to hoist smaller seasteading vessels from the water onto its spacious deck for repair and refit operations. See Mobile Crane Vessel (MCV).
Wale	A thicker strake, consisting of a wooden plank or group of planks, in the outer skin of the hull, running in a fore-and-aft direction, to provide extra stiffening in selected regions.
Wardroom	1. The living quarters of a naval ship that are designated for the use of commissioned officers other than the captain. 2. A collective term for the commissioned officers of a naval ship excluding her captain; e.g. "The captain rarely referred to his wardroom for advice, and this led to their discontent".
Warm the bell	Royal Navy slang from the Age of Sail for doing something unnecessarily or unjustifiably early. Holding a half-hour marine sandglass used until the early 19th century to time watches under one's coat or in one's hand to warm it allegedly expanded the glass′s neck to allow the sand to flow more quickly, justifying ringing the bell rung every half-hour to announce the passage of time on watch earlier than if the glass was cold, hence warming the bell and shortening the length of the watch.
Warp	1. To move a vessel by hauling on a line or cable that is fastened to an anchor or pier, especially so as to move a sailing ship through a confined or restricted space such as in a harbor. 2. A line or cable used in warping a ship.
Wash	The waves created by a moving vessel. Not to be confused with wake.
Washstrake	An additional strake fastened above the level of the gunwale of an open boat to increase the freeboard.
Watch	A period of time during which a part of the crew is on duty. Changes of watch are marked by strokes on the ship's bell.
Watchstanding	Also watchkeeping. The allocation of crew or staff to specific roles on a ship in order to operate it continuously. These assignments, known as watches, are divided into regularly scheduled work periods of several hours or longer to ensure that some portion of the crew is always occupying the roles at all times. Those members of the crew who are on watch at a given time are called watchkeepers.
Water bus	A watercraft used to provide transportation on a scheduled service with multiple stops, usually in an urban environment, analogous to the way a bus operates on land. It differs from a water taxi, which is a similar watercraft that provides transport service to various locations on demand rather than on a predetermined schedule, analogous to the way a taxicab operates on land, although in North America these terms are often used interchangeably. A water bus also differs from a ferry, which usually refers to a watercraft that shuttles between only two points.
Water kite	See paravane (definition 2).
Water sampling	devices range from a bucket dropped over the side of a ship to large water bottles sent thousands of meters toward the seafloor on a wire. Probably the most commonly used water sampler is known as a CTD /rosette: it is a framework designed to carry 12 to 36 sampling bottles (typically ranging from 1.2- to 30-liter capacity) and a conductivity / temperature/depth sensor that sends information to the laboratory so that the water bottles can be closed selectively as the instrument ascends. Alternatively a single water bottle can be equipped with a spring-loaded release and lowered on a line. When the desired depth is reached, a messenger weight is slid down the line and trips the release allowing, the end caps to snap close on the bottle. The largest water bottles, called Gerard barrels, collect 250 liters. Particles in the water samples may be quantified with a transmissometer sent down the wire or attached to a CTD /rosette. Aboard the ship, a flow cytometer may be used to analyze particles in the form of single-celled organisms for optical properties indicative of their physiology and structure.
Water taxi	A watercraft used to provide transportation on demand to various locations, usually in an urban environment, analogous to the way a taxicab operates on land. It differs from a water bus, which is a similar watercraft that provides transportation on a scheduled service with multiple stops rather than at the rider's will, analogous to the way a bus operates on land, although in North America these terms are often used interchangeably. A water taxi also differs from a ferry, which usually refers to a watercraft that shuttles between only two points.
Watercraft	Any vessel intended for transportation on water, e.g. ships, boats, personal watercraft, etc.
Waterline	The line where the hull of a ship meets the water's surface.
Watersail	A sail hung below the boom on gaff rig boats for extra downwind performance when racing.
Watertender	See fireman (definition 1).
Waterway	1. Any navigable body of water. 2. A strake of timber laid against the frames or bulwark stanchions at the margin of a laid wooden deck, usually about twice the thickness of the deck planking.
Wave Gauges	are made in several ways. Electric wave staffs measure wave height by changes in resistance. More common is using a pressure sensor with a current meters in a technique called PUV. Wave height is measured as changes in pressure. With an array of three or more sensors, wave direction can be determined. Another method uses Doppler current meters to form a virtual wave array. This is done by bottom mounting an upward-looking, multiplebeamed Doppler so it can measure the range to the surface as well as the orbital wave velocities in a series of bins extending away from the instrument. These mani fold measurements allow one to differentiate among multiple sources of waves—something that a single point sensor cannot do. ... (more at Wave Gauges)
Way
Way-landing	An intermediate stop along the route of a steamboat.
Way-lay	The verb's origin, from wegelage, means "lying in wait, with evil or hostile intent". So to be waylaid refers to a ship that has been taken off its course, route, or way by surprise, typically by unfortunate or nefarious means. In Herman Melville's 1851 novel Moby-Dick, the great white whale waylaid the Pequod and sank it, with only a few souls surviving in lifeboats.[97]
Waypoint	A location defined by navigational coordinates, especially as part of a planned route.
Ways	The timbers of shipyard stocks that slope into the water and along which a ship or large boat is launched. A ship undergoing construction in a shipyard is said to be on the ways, while a ship scrapped there is said to be broken up in the ways. Also known as a slipway.
Wearing ship	Tacking away from the wind in a square-rigged vessel. See also gybe.
Weather deck	A deck that is continually exposed to the weather – usually either the main deck or, in larger vessels, the upper deck.
Weather gage	Also weather gauge or weather-beam. Favorable position over another sailing vessel with respect to the wind.
Weather helm	The tendency of a sailboat to turn to windward in a strong wind when there is no change in the rudder's position. This is the opposite of lee helm and is the result of a dynamically unbalanced condition. See also center of lateral resistance.
Weather ship	A ship stationed in the ocean as a platform from which to record surface and upper-air meteorological observations for use in weather forecasting.
Weather side	Also windward side or simply windward. The side of a ship exposed to the wind, i.e. the side facing upwind or the direction from which the wind is blowing. Contrast lee side.
Weatherly	A ship that is easily sailed and maneuvered, or which makes little leeway when sailing to windward.
Weigh anchor	To heave up an anchor preparatory to sailing.
Well	A place in the ship's hold for pumps.
Well-found	Properly set up or provisioned.
Wet	(of a ship) Prone to taking water over her decks at sea. For example, a ship that tends to take water over her bow can be said to be "wet forward."
Wetted	The surface area that interacts with the working fluid or gas. The wetted area is the area of the hull of a watercraft which is immersed in water. This has a direct relationship on the overall hydrodynamic drag of the ship or submarine.
Wetted area	In sailboating, the portion of the hull immersed in water (i.e. below the waterline).
Whaleback	1. A type of cargo steamship of unusual design formerly used on the Great Lakes of North America, notably for carrying grain or ore. The hull continuously curved above the waterline from vertical to horizontal, and when the ship was fully loaded, only the rounded portion of her hull (the "whaleback" proper) was visible above the waterline. With sides curved in towards the ends, whalebacks had a spoon-shaped bow and a very convex upper deck. 2. A type of high-speed launch first designed for the Royal Air Force during World War II, or certain smaller rescue and research vessels most common in Europe that, like the Great Lakes vessels, have hulls that curve over to meet the deck, although the "whaleback" designation comes not from the curve along the gunwale as in the Great Lakes vessels, but from the fore-and-aft arch in the deck.
Whaleboat	1. A type of open boat that is relatively narrow and pointed at both ends, enabling it to move either forwards or backwards equally well. 2. On modern warships, a relatively light and seaworthy boat used for transport of the ship's crew.
Whaler	1. Also whaling ship. A specialized vessel designed for catching or processing whales. 2. A person engaged in the catching or processing of whales.
Wharf	A structure on the shore of a harbor or on the bank of a river or canal where ships may dock to load and unload cargo or passengers. Such a structure includes one or more berths (i.e. mooring locations), and may also include piers, warehouses, or other facilities necessary for handling the ships. The term "wharf" is generally synonymous with quay, although the solid foundations of a quay contrast with the closely spaced piles of a wharf. When "quay" and "wharf" are used as synonyms, the term "quay" is more common in everyday speech in the United Kingdom, many Commonwealth countries, and the Republic of Ireland, while "wharf" is more commonly used in the United States.
Wharfage	1. A collective term for docks, piers, quays, and wharfs. 2. A collective term for all wharfs in a given port, area, country, region, etc.
Wheel	Also ship's wheel. The usual steering device on larger vessels: a wheel with a horizontal axis, connected by cables to the rudder.
Wheelhouse	Also pilothouse and often synonymous with bridge. The location on a ship where the wheel is located.
Whelkie	A small sailing pram.
Wherry	A type of boat traditionally used for carrying cargo or passengers on rivers and canals in England, particularly on the River Thames and the Norfolk and Suffolk Broads.
Whiff	A chiefly British term for a narrow clinker-built skiff having outriggers and designed for one oarsman.
Whip	A small single block tackle, used to raise light loads from a hold.
Whip upon whip	Connecting two whips together. This runs more smoothly than using a double block with single block tackle, which would have the equivalent purchase. Can be used for topsail and top-gallant halliards.
Whipping	The binding with twine of the loose end of a rope to prevent it unraveling.
Whipstaff	A vertical lever connected to a tiller, used for steering on larger ships before the development of the ship's wheel.
Whiskers	Spreaders from the bow to spread the bowsprit shrouds.
Whiskerstay	One of the pair of stays that stabilize the bowsprit, horizontally affixed to the forward end of the bowsprit and just aft the stem.
White Ensign	A British flag flown as an ensign by certain British ships. Prior to 1864, ships of the Royal Navy′s White Squadron flew it; since the reorganization of the Royal Navy in 1864, it has been flown by all Royal Navy ships and shore establishments, yachts of members of the Royal Yacht Squadron, and ships of Trinity House escorting the reigning monarch of the United Kingdom.
White horses	Also whitecaps. Foam or spray on wave tops caused by stronger winds (usually above Force 4).
Williamson turn	A type of man overboard rescue turn. Other variations include the Anderson turn, the quick turn, and the Scharnow turn.
Winch	A mechanical device for pulling on a rope (such as a sheet or halyard), usually equipped with a pawl to assist in control. It may be hand-operated or powered.
Winches	are devices used to pay out, pull in, and store cable. They consist of a movable drum around which a cable is wound so that rotation of the drum produces a drawing force at the end of the cable. Winches can be powered by diesel, hydraulic or electrical power. A reel is a handpowered winch. Winches are selected by cable capacity, line speed, strength (line pull) and material (typically steel or aluminum). Options include remote controls, level winds, variable speed drives, brakes, clutches (for free spooling), cable counters and heave compensation. There are many special types of winches for specific applications, including those for ROV umbilicals, diver hoses, and CTDs . Slip rings are used with winches to transfer electrical power. Other related devices include: • Traction Winches are used for tensioning the cable so there will be no spooling problems due to slack line. ... (more at Winches)
Wind-over-tide	Sea conditions in which a tidal current and a wind are moving in opposite directions, leading to short, heavy seas.
Windage	The wind resistance of a boat.
Windbound	A condition wherein a ship is detained in one particular station by contrary winds.
Winding tackle	A tackle formed of two triple blocks or a triple and a double, used to raise heavy loads such as guns and anchors.
Windjammer	A large iron- or steel-hulled square-rigged sailing ship of the late 19th and early 20th centuries with three, four, or five masts, built mainly between the 1870s and 1900 to carry cargo on long voyages.
Windlass	A winch mechanism, usually with a horizontal axis, designed to move very heavy loads. Used where mechanical advantage greater than that obtainable by block and tackle was needed (such as raising the anchor on small ships).
Windsail	A wide tube or funnel of canvas used to convey a stream of air into the lower compartments of a ship for ventilation.
Windward	In the direction that the wind is coming from. Contrast leeward.
Wing	An extension on the side of a vessel, e.g. a bridge wing is an extension of the bridge to both sides, intended to allow bridge personnel a full view to aid in the maneuvering of the ship.
Wiper	The most junior rate among personnel who work in the engine room of a ship, responsible for cleaning the engine spaces and machinery and assisting the engineers as directed. A wiper is often serving an apprenticeship to become an oiler.
Working up	Training on a warship to achieve the best possible effectiveness, usually after commissioning or a refit.
Works	Shipyards, drydocks and other specialized construction, refit or repair facilities for vessels.
Worm, parcel and serve	Often collectively called service. To apply a multilayered protection against chafing and deterioration to a section of line by laying yarns to fill in the cuntlines (worming), wrapping marline or other small stuff around it (serving), and stitching a covering of canvas over all (parceling). It can be applied to the entire length of a line, such as a shroud, or selectively to specific parts of a line, such as over the spliced ends of a stay, where the chafe on the middle section of the stay precludes complete protection.
Wrecking tug	Another name for a salvage tug.
Xebec	Variously spelled zebec, xebeck, xebeque, xebecque, zebeck, zebecque, chebec, or shebeck. 1. A Mediterranean sailing ship, usually employed for trading, that is propelled by a combination of lateen sails and oars and characterized by a distinctive hull with a pronounced overhanging bow and stern; early xebecs had two masts and later ones had three.
Xebec-frigate	A European warship that appeared late in the history of the xebec. It was fully square-rigged but otherwise designed like an ordinary xebec. X.O. (or XO)
Yacht	Any boat or ship designed specifically for recreational use. The term includes sailing yachts, motor yachts, and steam yachts.
Yar	(of a vessel, especially a sailing vessel) Quick, agile, and easy to steer, hand, and reef.
Yard	1. A horizontal spar from which a square sail is suspended. 2. The spar on which a lugsail or Gunter sail is set.
Yard name	The name initially given to a ship during its construction. The yard name may or may not be the same as the officially registered name, which is provided after completion of the vessel.
Yard number	The number assigned to a ship built by a particular shipyard. Each shipyard typically numbers the ships that it has built in consecutive order. One use is to identify the ship before a name has been chosen.
Yard tackle	Tackle used to raise boats.
Yardarm	The very end of a yard. Often mistaken for the yard itself, which refers to the entire spar. As in to hang "from the yardarm" and the sun being "over the yardarm" (late enough to have a drink).
Yarr	Acknowledgement of an order, or agreement. Also aye, aye.
Yaw	A vessel's rotational motion about the vertical axis, causing the fore and aft ends to swing from side to side repetitively.
Yawl	1. A fore-and-aft-rigged sailing vessel with two masts, main and mizzen, the mizzen stepped abaft the rudder post. 2. An un-decked boat, often beach-launched, worked under both oar and sail, and generally clinker-built. Used for fishing, serving ships in anchorages, salvage work, etc. Those from the northern parts of Britain tended to be double-ended.
Yawl boat	A rowboat on davits at the stern of the boat.
Yeoman	A U.S. Navy enlisted rating (YN) responsible for administrative duties.
Zebec	An alternative spelling of xebec.
Zulu