Pronunciation: (kā'sun, -son),[key] —n. 1. a structure used in underwater work, consisting of an airtight chamber, open at the bottom and containing air under sufficient pressure to exclude the water.
2. a boatlike structure used as a gate for a dock or the like.
3. Naut. a. Also called camel, pontoon. a float for raising a sunken vessel, sunk beside the vessel, made fast to it, and then pumped out to make it buoyant.
b. a watertight structure built against a damaged area of a hull to render the hull watertight; cofferdam.
4. a two-wheeled wagon, used for carrying artillery ammunition.
5. an ammunition chest.
6. a wooden chest containing bombs or explosives, used formerly as a mine.
7. Archit.coffer (def. 4).