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.
3. (v.) To move or adjust a sail by manual force (i.e. directly with the hands) rather than by using running rigging.
4. (v.) A term used since the end of the 17th century for the action of a strong, favorable current on a sailing vessel allowing her to make good progress despite insufficient wind for sailing; the vessel is considered to be horsed by the current, riding it in the way a human rides a horse.