crustaceanPronunciation: /krʌˈsteɪʃn/ ZoologyTranslate crustacean | into Italian | into Spanish Definition of crustacean noun an arthropod of the large, mainly aquatic group Crustacea, such as a crab, lobster, shrimp, or barnacle. adjective relating to or denoting crustaceans. Derivatives crustaceous adjective crustacean in other Oxford dictionaries Definition of crustacean in the US English dictionary