Definition of crab

• n. - One of the brachyuran Crustacea. They are mostly marine, and usually have a broad, short body, covered with a strong shell or carapace. The abdomen is small and curled up beneath the body.
• n. - The zodiacal constellation Cancer.
• a. - A crab apple; -- so named from its harsh taste.
• a. - A cudgel made of the wood of the crab tree; a crabstick.
• a. - A movable winch or windlass with powerful gearing, used with derricks, etc.
• a. - A form of windlass, or geared capstan, for hauling ships into dock, etc.
• a. - A machine used in ropewalks to stretch the yarn.
• a. - A claw for anchoring a portable machine.
• v. t. - To make sour or morose; to embitter.
• v. t. - To beat with a crabstick.
• v. i. - To drift sidewise or to leeward, as a vessel.
• a. - Sour; rough; austere.