The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mottle \Mot"tle\, n.
   A mottled appearance.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mottle
    n 1: an irregular arrangement of patches of color; "it was not
         dull grey as distance had suggested, but a mottle of khaki
         and black and olive-green"
    v 1: mark with spots or blotches of different color or shades of
         color as if stained [syn: mottle, streak, blotch]
    2: colour with streaks or blotches of different shades [syn:
       mottle, dapple, cloud]