The Collaborative International Dictionary of English v.0.48:

Horsy \Hors"y\, a.
   Pertaining to, or suggestive of, a horse, or of horse racing;
   as, horsy manners; garments of fantastically horsy fashions.
   [Colloq.]
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "horsy":
   asinine, bovid, bovine, caprid, caprine, cowish, cowlike, deerlike,
   equestrian, equine, goatish, goatlike, hircine, hoggish, hoofed,
   mulish, ovine, piggish, ruminant, sheepish, sheeplike, swinish,
   ungulate