- noun sea animals such as crabs and oysters which have a hard outer covering and which you can eat
- noun a sea animal that has a hard shell and is used as food
- The collective name for a group of generally sea-dwelling creatures comprising molluscs, cephalopods and crustaceans. Oysters, squid and lobsters are typical examples. The only freshwater shellfish is the crayfish which is a crustacean.
- noun animals such as mussels, oysters, lobsters, and prawns, which have shells and live in them