The Collaborative International Dictionary of English v.0.48:

Piebald \Pie"bald`\, a. [Pie the party-colored bird + bald.]
   1. Having spots and patches of black and white, or other
      colors; mottled; pied. "A piebald steed of Thracian
      strain." --Dryden.
      [1913 Webster]

   2. Fig.: Mixed. "Piebald languages." --Hudibras.
      [1913 Webster]

WordNet (r) 3.0 (2006):

piebald
    adj 1: having sections or patches colored differently and
           usually brightly; "a jester dressed in motley"; "the
           painted desert"; "a particolored dress"; "a piebald
           horse"; "pied daisies" [syn: motley, calico,
           multicolor, multi-color, multicolour, multi-
           colour, multicolored, multi-colored,
           multicoloured, multi-coloured, painted,
           particolored, particoloured, piebald, pied,
           varicolored, varicoloured]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "piebald":
   bay, bayard, buckskin, calico, calico pony, chestnut, clouded,
   dapple, dapple-gray, dappled, dun, gray, grizzle, marbled, motley,
   mottled, paint, painted pony, pepper-and-salt, pied, pinto, roan,
   skewbald, sorrel