noun (n)

• meat of edible aquatic invertebrate with a shell (especially a mollusk or crustacean)(noun.food)

  source: wordnet30
• invertebrate having a soft unsegmented body usually enclosed in a shell(noun.animal)

  Synonym:
  mollusc, mollusk
  

  source: wordnet30
• Any aquatic animal whose external covering consists of a shell, either testaceous, as in oysters, clams, and other mollusks, or crustaceous, as in lobsters and crabs.(noun)

  source: webster1913