WordNet (r) 3.0 (2006):
ahorse adv 1: on the back of a horse; "he rode horseback to town"; "managed to escape ahorse"; "policeman patrolled the streets ahorseback" [syn: horseback, ahorse, ahorseback] adj 1: traveling on horseback; "a file of men ahorseback passed by" [syn: ahorse(p), ahorseback(p)]