defining (Noun) — Any process serving to define the shape of something.
defining (Verb) — Determine the essential quality of.
defining (Verb) — Give a definition for the meaning of a word. ex. "Define 'sadness'"
defining (Verb) — Determine the nature of. ex. "What defines a good wine?"
defining (Verb) — Show the form or outline of. ex. "The camera could define the smallest object" ex. "The tree was clearly defined by the light"
defining (Verb) — Decide upon definitely; give a value. ex. "define the parameters"