The Collaborative International Dictionary of English v.0.48:

Dapple \Dap"ple\, Dappled \Dap"pled\, a.
   Marked with spots of different shades of color; spotted;
   variegated; as, a dapple horse.
   [1913 Webster]

         Some dapple mists still floated along the peaks. --Sir
                                                  W. Scott.
   [1913 Webster]

   Note: The word is used in composition to denote that some
         color is variegated or marked with spots; as,
         dapple-bay; dapple-gray.
         [1913 Webster]

               His steed was all dapple-gray.     --Chaucer.
         [1913 Webster]

               O, swiftly can speed my dapple-gray steed. --Sir
                                                  W. Scott.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dapple \Dap"ple\, v. t. [imp. & p. p. Dappled; p. pr. & vb. n.
   Dappling.]
   To variegate with spots; to spot.
   [1913 Webster]

         The gentle day, . . .
         Dapples the drowsy east with spots of gray. --Shak.
   [1913 Webster]

         The dappled pink and blushing rose.      --Prior.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dappled
    adj 1: having spots or patches of color [syn: dappled,
           mottled]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "dappled":
   Quaker-colored, acier, amalgamated, ambiguous, ambivalent,
   amphibious, ashen, ashy, blended, calico, canescent, cinereous,
   cinerous, clouded, combined, complex, composite, compound,
   compounded, conglomerate, dapple, dapple-gray, dappled-gray, dingy,
   discolor, dismal, dove-colored, dove-gray, dreary, dull, dusty,
   eclectic, equivocal, fifty-fifty, glaucescent, glaucous, gray,
   gray-black, gray-brown, gray-colored, gray-drab, gray-green,
   gray-spotted, gray-toned, gray-white, grayed, grayish, griseous,
   grizzle, grizzled, grizzly, half-and-half, heterogeneous,
   indiscriminate, intricate, iron-gray, ironic, jumbled, lead-gray,
   leaden, livid, many-sided, marbled, medley, mingled, miscellaneous,
   mixed, motley, mottled, mouse-colored, mouse-gray, mousy,
   multicolor, multicolored, multifaceted, multihued, multinational,
   multiracial, parti-colored, patchy, pearl, pearl-gray, pearly,
   pepper-and-salt, piebald, pied, pinto, pluralistic, promiscuous,
   sad, scrambled, silver, silver-gray, silvered, silvery, skewbald,
   slate-colored, slaty, smoke-gray, smoky, sober, somber, steel-gray,
   steely, stone-colored, syncretic, taupe, thrown together,
   varicolored, varied, versicolor, versicolored