- Any of various crabs belonging to a group within the order Decapoda that protect their soft, unarmored abdomens by occupying and carrying about the empty shells of snails or other univalve mollusks.寄居蟹：属于十足目动物某一群的任何一种蟹，该蟹占据或背负蜗牛或其它单壳软体动物的空壳来保护其柔软无甲的腹部