any of a subphylum (Crustacea) of arthropods, including shrimps, crabs, barnacles, and lobsters, that usually live in the water and breathe through gills: they have a hard outer shell and jointed appendages
adjective
of crustaceans
See crustacean in American Heritage Dictionary 4
crus·ta·cean
noun
Any of various predominantly aquatic arthropods of the class Crustacea, including lobsters, crabs, shrimps, and barnacles, characteristically having a segmented body, a chitinous exoskeleton, and paired, jointed limbs.
adjective
Of or belonging to the Crustacea.
Origin: From New Latin Crūstācea, class name, neuter pl. of crūstāceus, hard-shelled, from Latin crūsta, shell; see kreus- in Indo-European roots.