crab(redirected from catch a crab)
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1. A crustacean, many varieties of which are edible.
2. An insect, the crab louse, Pthirus pubis.
a. Any of various chiefly marine decapod crustaceans of the infraorder Brachyura, having a hard carapace that covers a broad flattened cephalothorax with a small abdomen tucked beneath it, and an anterior pair of legs that are large and pincerlike.
b. Any of various similar decapod crustaceans, such as a hermit crab or a king crab.
a. A crab louse.
b. crabs Slang Infestation by crab lice.