The definition of a crustacean is an arthropod with a hard outer shell and jointed limbs that usually lives in aquatic environments.
A lobster is an example of a crustacean.
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
Origin of crustaceanModern Latin Crustacea from crustaceus, having a crust or shell from Classical Latin crusta, crust
Any of various predominantly aquatic arthropods of the subphylum (or class) Crustacea, including lobsters, crabs, shrimps, and barnacles, characteristically having a segmented body, a chitinous exoskeleton, paired jointed limbs, and two pairs of antennae.
Origin of crustaceanFrom New Latin Crūstācea class name neuter pl. of crūstāceus hard-shelled from Latin crusta shell ; see kreus- in Indo-European roots.
(plural crustaceans or crustacea)