One of the two main classifications of shellfish (the other being crustacean), mollusks are invertebrates with soft bodies covered by a shell of one or more pieces. Mollusks are further divided into...
crayfish : early 14c., crevis, from O.Fr. crevice "crayfish" (13c., Mod.Fr. écrevisse), probably from Frankish *krebitja or a similar Germanic word that is a dim. form of the root of crab (1); e.g....
Any of numerous chiefly marine invertebrates of the phylum Mollusca, typically having a soft unsegmented body, a mantle, and a protective calcareous shell and including the edible shellfish and the...