How do you spell Equestrian

Available Definitions:
1)  a. - Of or pertaining to horses or horsemen, or to horsemanship; as, equestrian feats, or games.
2)  a. - Being or riding on horseback; mounted; as, an equestrian statue.
3)  a. - Belonging to, or composed of, the ancient Roman equities or knights; as, the equestrian order.
4)  n. - One who rides on horseback; a horseman; a rider.