n. pl. shellfish or
shell·fish·es 1. Any of various edible aquatic invertebrate animals having a shell, especially mollusks such as clams and oysters, and crustaceans such as lobsters, crabs, and shrimp.
2. An edible mollusk, in contrast to a crustacean: regulations concerning fish, crustaceans, and shellfish.
3. The edible flesh of such animals.