‖n. pl. [ NL., fr. Gr. 'o`strakon shell of a testacean. ] (Zool.) A division of bivalve mollusks including the oysters and allied shells. [ 1913 Webster ]

n. [ L. ostrea an oyster. See Oyster. ] (Zool.) Any one of a family of bivalves, of which the oyster is the type. [ 1913 Webster ]