a small shellfish that attaches itself to objects underwater, for example to rocks and the bottoms of ships 藤壶（小甲壳动物，附着于水下岩石或船底等） Word Originlate 16th cent.: from medieval Latin bernaca, of unknown origin. In Middle English the term denoted the barnacle goose, whose breeding grounds were then unknown and which was thought to hatch from the shell of the crustacean to which it gave its name.