n pl 1  cap  :  a large class of mostly aquatic arthropods that have a chitinous or calcareous and chitinous exoskeleton, a pair of often much modified appendages on each segment, and two pairs of antennae and that include the lobsters, shrimps, crabs, wood lice, water fleas, and barnacles  2  :  arthropods of the class Crustacea crus*ta*cean adj or n 
 
 
 
Similar sounding terms:  Cri·ce·tus 
 
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