1.verbTo determine with precision; to mark out with distinctness; to ascertain or exhibit clearly.
"the defining power of an optical instrument"
2.verbTo settle, decide (an argument etc.)
3.verbTo express the essential nature of something.
"I define myself as a techno-anarchist."
4.verbTo state the meaning of a word, phrase, sign, or symbol.
"The textbook defined speed as velocity divided by time."
5.verbTo 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.
"Person 1: Is she good at math?"
6.verbTo demark sharply the outlines or limits of an area or concept.
"to define the legal boundaries of a property"
7.verbTo establish the referent of a term or notation.