A Beef

(uncountable) The meat from a cow, bull, or other bovine.

(in the meat industry, on product packaging) The edible portions of a cow (including those which are not meat).
(uncountable) Bovine animals.
(archaic, countable, plural: beeves) A single bovine (cow or bull) being raised for its meat.
(by extension, slang, uncountable) Muscle or musculature; size, strength or potency.
(figuratively, slang, uncountable) Essence, content; the important part of a document or project.

(slang, countable or uncountable, plural: beefs) A grudge; dislike (of something or someone); lack of faith or trust (in something or someone); a reason for a dislike or grudge. (often + with)
Remember what happened last fall?

Synonyms

(meat of a cow): cowflesh

(meat of an ox): oxflesh

Hyponyms

(meat of a cow): veal