Defining

To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly.

"the defining power of an optical instrument"

To settle, decide (an argument etc.)

To express the essential nature of something.

"I define myself as a techno-anarchist."

To state the meaning of a word, phrase, sign, or symbol.

"The textbook defined speed as velocity divided by time."

Serving to define or distinguish.

"The ability to reproduce is a defining characteristic of living organisms."