crab

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.
• noun Any of various similar decapod crustaceans, such as a hermit crab or a king crab.
• noun Crabmeat.
• noun A crab louse.
• noun Slang Infestation by crab lice.
• noun The maneuvering of an aircraft partially into a crosswind to compensate for drift.
• noun A machine for handling or hoisting heavy weights.
• intransitive verb To hunt or catch crabs.
• intransitive verb To scurry sideways in the manner of a crab.
• intransitive verb To drift diagonally or sideways, especially when under tow.
• intransitive verb To direct an aircraft into a crosswind.
• intransitive verb To direct (an aircraft) partly into a crosswind to eliminate drift.
• intransitive verb To cause to move or scurry sideways.
• idiom (catch a crab) To make a faulty stroke in rowing that causes the blade of the oar to strike the water on the recovery stroke.
• noun A crabapple tree or its fruit.
• noun A quarrelsome, ill-tempered person.
• intransitive verb To find fault; criticize someone or something.
• intransitive verb Informal To interfere with and ruin; spoil.
• intransitive verb Informal To find fault with; complain about.
• intransitive verb To make ill-tempered or sullen.

from The Century Dictionary.

• To fish for or catch crabs: as, to go crabbing.
• Figuratively, to act like a crab in crawling backward; back out; “crawfish”: as, he tried to crab out of it.
• noun A crabbed, sour-tempered, peevish, morose person.
• Sour; rough; harsh to the taste.
• To irritate; fret; vex; provoke; make peevish, cross, sour, or bitter, as a person or his disposition; make crabbed.
• To break or bruise.
• To be peevish or cross.
• In falconry, to seize each other when fighting: said of hawks.
• noun Iu Australia, the marine crustacean, Scylla serrata; also, Telphusa transversa, a crustacean found in fresh water.
• noun plural Same as crabyaws.
• noun A cliff-crab, especially Grapsus pictus.
• noun A popular name for all the stalk-eyed, ten-footed, and short-tailed or soft-tailed crustaceans constituting the subclass Podophthalmia, order Decapoda, and suborders Brachyura and Anomura: distinguished from lobsters, shrimps, prawns, crawfish, and other long-tailed or macrurous crustaceans, by shortness of body, the abdomen or so-called tail being reduced and folded under the thorax and constituting the apron, or otherwise modified. See cut under Brachyura.
• noun Some crustacean likened to or mistaken for a crab: as, the glass-crabs; the king-crabs. See the compounds.
• noun A crab-louse.
• noun Cancer, a constellation and sign of the zodiac. See Cancer
• noun An arch.
• noun plural The lowest cast at hazard.
• noun A name of various machines and mechanical contrivances.
• noun Among professional oarsmen, to sink the oar-blade so deeply in the water that it cannot he lifted easily, and hence tends to throw the rower out of the boat.
• To ‘pull to pieces’; criticize or find fault with; hence, to hinder, spoil or defeat by adverse criticism of trivial details.
• noun A small, tart, and somewhat astringent apple, of which there are several varieties, cultivated chiefly for ornament and to be made into preserves, jelly, etc.; the crab-apple.
• noun The tree producing the fruit.
• noun A walking-stick or club made of the wood of the crab-apple; a crabstick.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb (Naut.) To drift sidewise or to leeward, as a vessel.
• adjective Sour; rough; austere.
• transitive verb obsolete To make sour or morose; to embitter.