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.
[From New Latin Crūstācea, class name, neuter pl. of crūstāceus, hard-shelled, from Latin crusta, shell; see kreus- in the Appendix of Indo-European roots.]
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