Source : Webster's Revised Unabridged Dictionary (1913)

Defiance \De*fi"ance\, n. [OF. defiance, desfiance, challenge,
   fr. desfier to challenge, F. d['e]fier. See {Defy}.]
   1. The act of defying, putting in opposition, or provoking to
      combat; a challenge; a provocation; a summons to combat.

            A war without a just defiance made.   --Dryden.

            Stood for her cause, and flung defiance down.
                                                  --Tennyson.

   2. A state of opposition; willingness to flight; disposition
      to resist; contempt of opposition.

            He breathed defiance to my ears.      --Shak.

   3. A casting aside; renunciation; rejection. [Obs.]
      ``Defiance to thy kindness.'' --Ford.

   {To bid defiance}, {To set at defiance}, to defy; to
      disregard recklessly or contemptuously. --Locke.

Source : WordNet®

defiance
     n 1: intentionally contemptuous behavior or attitude [syn: {rebelliousness}]
     2: a hostile challenge
     3: a defiant act