e·ques·tri·an 
(ĭ-kwĕstrē-ən)
(ĭ-kwĕstrē-ən)adj.
1. Of or relating to horseback riding or horseback riders.
2. Depicted or represented on horseback: an equestrian statue of a famous monarch.
n.
One who rides a horse or performs on horseback.
[From Latin equester, equestr-, from eques, horseman, from equus, horse; see ekwo- in the Appendix of Indo-European roots.]
e·questri·an·ism, e·questri·an·ship n.