Source : Webster's Revised Unabridged Dictionary (1913)

Denature \De*na"ture\, v. t. [De- + nature.]
   To deprive of its natural qualities; change the nature of.

Source : WordNet®

denature
     v 1: add nonfissionable material to (fissionable material) so as
          to make unsuitable for use in an atomic bomb
     2: modify (as a native protein) especially by heat, acid,
        alkali, or ultraviolet radiation so that all of the
        original properties are removed or diminished
     3: make (alcohol) unfit for drinking without impairing
        usefulness for other purposes