WordWeb Online

1. An ornamental sunken panel in a ceiling or dome
   - coffer, lacuna
    
2. A two-wheeled military vehicle carrying artillery ammunition
    
3. A chest to hold ammunition
   - ammunition chest
    
4. Large watertight chamber used for construction under water
   - pneumatic caisson, cofferdam

Derived forms: caissons

Type of: chamber, chest, military vehicle, panel

Encyclopedia: Caisson