n (context|engineering) An enclosure, from which water can be expelled, in order to give access to underwater areas for engineering works etc.
n (nautical) A floating tank that can be submerged, attached to an underwater object and then pumped out to lift the object by buoyancy; a camel.
n (military) A two-wheeled, horse-drawn military vehicle used to carry ammunition (and a coffin at funerals).