Source : Webster's Revised Unabridged Dictionary (1913)

Discoloration \Dis*col`or*a"tion\, n. [Cf. F. decoloration.]
   1. The act of discoloring, or the state of being discolored;
      alteration of hue or appearance. --Darwin.

   2. A discolored spot; a stain. --Arbuthnot.

Source : WordNet®

discoloration
     n 1: a soiled or discolored appearance; "the wine left a dark
          stain" [syn: {stain}, {discolouration}]
     2: the act of changing the natural color of something by making
        it duller or dingier or unnatural or faded [syn: {discolouration}]