noun

• (semantics, lexicography) A statement of the meaning of a word, word group, sign, or symbol; especially, a dictionary definition.
  "Your definition of "elephant" needs to be more precise than "a big animal with large ears"."
• (usually with the definite article the) A clear instance conforming to the dictionary or textbook definition.
  "Baroque is a good game, but only for a very narrow subset of the gaming audience. It is the very definition of a niche title."
• (bodybuilding) The degree to which individual muscles are distinct on the body.
• (programming) A statement which provides a previous declaration with a value or body of a subroutine (in the case of function).