1. A crustacean, many varieties of which are edible. 2. An insect, the c. louse, Pthirus pubis.
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crab 'krab n
1) any of a tribe (Brachyura) of chiefly marine crustaceans with a short broad usu. flattened carapace, a small abdomen that curls forward beneath the body, short antennae, and the anterior pair of limbs modified as grasping pincers
2) crabs pl infestation with crab lice
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(krab) 1. any of various mollusks of the order Decapoda; see also Potamon. 2. a vernacular term for Phthirus pubis.Medical dictionary. 2011.