Definition of defines:
(v) :
To state the meaning of a word, phrase, sign, or symbol.
(v) :
To express the essential nature of something.
(v) :
To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly.
(v) :
To describe, explain, or make definite and clear; used to request the listener or other person to elaborate or explain more clearly his or her intended meaning of a word or expression.
(v) :
To demark sharply the outlines or limits of an area or concept.
(v) :
(mathematics) To establish the referent of a term or notation.