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.
3. On marine seismic survey vessels, the lowest deck on the ship, which carries the seismic source arrays, consists of air guns arranged in clusters.
4. In naval slang, to fabricate or falsify something; in modern usage, meaning especially to falsify documentation in order to avoid doing work or make present conditions seem acceptable without having made a real effort to improve them.