The Collaborative International Dictionary of English v.0.48:

Pinto \Pin"to\, a. [Sp., painted.]
   Lit., painted; hence, piebald; mottled; pied.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Pinto \Pin"to\, n.
   Any pied animal; esp., a pied or "painted" horse.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Pintos \Pin"tos\, n. pl.; sing. Pinto. [Sp., painted,
   mottled.] (Eyhnol.)
   A mountain tribe of Mexican Indians living near Acapulco.
   They are remarkable for having the dark skin of the face
   irregularly spotted with white. Called also speckled
   Indians.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pinto
    n 1: a spotted or calico horse or pony

Moby Thesaurus II by Grady Ward, 1.0:

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