1. 1. A full-grown steer, bull, ox, or cow, especially one intended for use as meat.
   2. The flesh of a slaughtered full-grown steer, bull, ox, or cow.
2. Informal Human muscle; brawn.
3. pl. beefs Slang A complaint.

Word History: That beef comes from cows is known to most, but the close relationship between the words beef and cow is hardly household knowledge. Cow comes via Middle English from Old English cū, which is descended from the Indo-European root *g^wou-, also meaning "cow." This root has descendants in most of the branches of the Indo-European language family. Among those descendants is the Latin word bōs, "cow," whose stem form, bov-, eventually became the Old French word buef, also meaning "cow." The French nobles who ruled England after the Norman Conquest of course used French words to refer to the meats they were served, so the animal called cū by the Anglo-Saxon peasants was called buef by the French nobles when it was brought to them cooked at dinner. Thus arose the distinction between the words for animals and their meat that is also found in the English word-pairs swine/pork, sheep/mutton, and deer/venison. What is interesting about cow/beef is that we are in fact dealing with one and the same word, etymologically speaking.