noun a chest to hold ammunition.
2. caisson ·noun a sunk panel of ceilings or soffits.
3. caisson ·noun a structure, usually with an air chamber, placed beneath a vessel to lift or float it.
4. caisson ·noun a hollow floating box, usually of iron, which serves to close the entrances of docks and basins.
5. caisson ·noun a chest filled with explosive materials, to be laid in the way of an enemy and exploded on his approach.
6. caisson ·noun a water-tight box, of timber or iron within which work is carried on in building foundations or structures below the water level.
7. caisson ·noun a four-wheeled carriage for conveying ammunition, consisting of two parts, a body and a limber. in light field batteries there is one caisson to each piece, having two ammunition boxes on the body, and one on the limber.