WordNet (r) 3.0 (2006):

steeplechaser
    n 1: a horse trained to run in steeplechases

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "steeplechaser":
   broncobuster, buckaroo, caballero, cavalier, cavalryman, chevalier,
   circus rider, cowboy, cowgirl, cowpuncher, entry, equestrian,
   equestrienne, favorite, gaucho, horse soldier, horseback rider,
   horsebacker, horseman, horsewoman, jockey, knight,
   mounted policeman, mudder, plate horse, plater, pole horse, pony,
   postboy, postilion, puncher, race horse, racer, rider, roughrider,
   stable, stake horse, staker, starter, string, trick rider,
   vaquero