equestrian

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Of or relating to horseback riding or horseback riders.
• adjective Depicted or represented on horseback.
• noun One who rides a horse or performs on horseback.

from The Century Dictionary.

• Pertaining or relating to horses or horsemanship; concerned with horses or riding; consisting in or accompanied with performances on horseback: as, a person of equestrian tastes; an equestrian picture; equestrian feats, exercise, or sports.
• Riding or represented as riding on a horse; exercising or mounted on horseback: as, equestrian performers; an equestrian statue of Washington.
• Of or pertaining to the Roman equites or knights: as, the equestrian order. See equites.
• noun A rider on horseback; specifically, one who earns his living by performing feats of agility and skill on horseback in a circus.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who rides on horseback; a horseman; a rider.
• adjective Of or pertaining to horses or horsemen, or to horsemanship.
• adjective Being or riding on horseback; mounted.
• adjective Belonging to, or composed of, the ancient Roman equities or knights.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective of horseback riding or horseback riders
• noun an equestrian person; a horserider

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a man skilled in equitation
• adjective of or relating to or featuring horseback riding
• adjective of or relating to or composed of knights