a royal sacrifice in which a king would let loose a consecrated horse, protected by an army, to move about at its free will as a challenge to other kings and it would be brought back after a year when the king would be consecrated as an emperor of the region in which the horse moved unchallenged; a horse-sacrifice.

(loosely) a horse race for betting.

= ಅಶ್ವಮೇಧ - 1.