Source : Webster's Revised Unabridged Dictionary (1913)

Mottle \Mot"tle\, v. t. [imp. & p. p. {Mottled}; p. pr. & vb. n.
   {Mottling}.] [From {Mottled}.]
   To mark with spots of different color, or shades of color, as
   if stained; to spot; to maculate.

Mottle \Mot"tle\, n.
   A mottled appearance.

Source : WordNet®

mottle
     v 1: mark with spots or blotches of different color or shades of
          color as if stained [syn: {streak}, {blotch}]
     2: colour with streaks or blotches of different shades [syn: {dapple},
         {cloud}]