cais ‧ son /ˈkeɪs ə n, kəˈsuːn $ ˈkeɪsɑːn, -s ə n/ BrE AmE noun [countable]
[ Date: 1600-1700 ; Language: French ; Origin: caisse 'box' , from Latin capsa ; ⇨ ↑ case 1 ]
1 . a large box filled with air, that people go into to work under water, for example when building bridges
2 . a large box for carrying ↑ ammunition