I. noun
: a large anomuran land crab ( Birgus latro ) that is widely distributed about islands of the tropical Indian and Pacific oceans where it burrows in the soil and feeds on coconuts and is related to the hermit crabs but distinguished by its large size and its broad symmetrical abdomen the oily flesh of which is esteemed a delicacy by natives of the region — called also palm crab, robber crab, tree crab
II. noun
: any of the family Leucosiidae of crabs characterized by a granular carapace and long claws and by an adult female having the abdomen formed into a hemispherical cup that snaps shut against the sternum to form a brood chamber for the eggs ; especially : one ( Persephona mediterranea ) that occurs in shallow water along the Atlantic coast of Mexico and of the United States as far north as New Jersey