The Collaborative International Dictionary of English v.0.48:

Caballo \Ca*bal"lo\ (k[.a]*v[aum]l"y[-o]; 220), n. [Written also
   cavallo.] [Sp., fr. L. caballus a nag. See Cavalcade.]
   A horse. [Sp. Amer.]
   [Webster 1913 Suppl.]