caissons is a form of:

Caisson



noun
1.
(A watertight box or chamber inside which work can be carried out, a wheeled vehicle for transporting artillery shells, ammunition wagon, a float used to raise sunken vessels) ឃ្លប់ដែលមានឧបករណ៍គ្រប់យ៉ាងសម្រាប់ចុះទៅធ្វើការស្រាវជាវក្រោមទឹក, រទេះផ្ទុកស្បៀងឬយុទ្ធភ័ណ្ឌ, ក្រង់រទេះ, លូដែកសម្រាប់ធ្វើសំណង់ក្នុងទឹក, ទំនប់បាចពង្រីងទឹក, soldier's caisson ហិបអាវុធ, រថផ្ទុកអាវុធ
ENGLISH MEANING
noun
1.
A chest to hold ammunition.
2.
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.
3.
A chest filled with explosive materials, to be laid in the way of an enemy and exploded on his approach.
4.
A water-tight box, of timber or iron within which work is carried on in building foundations or structures below the water level.
5.
A hollow floating box, usually of iron, which serves to close the entrances of docks and basins.
6.
A structure, usually with an air chamber, placed beneath a vessel to lift or float it.
7.
A sunk panel of ceilings or soffits.