Horseback
Pronunciation : Horse"back`
Part of Speech : n.
Definition : 1. The back of a horse.
2. An extended ridge of sand, gravel, and bowlders, in a half- stratified condition. Agassiz. On horseback, on the back of a horse; mounted or riding on a horse or horses; in the saddle. The long journey was to be performed on horseback. Prescott.
Source : Webster's Unabridged Dictionary, 1913