horseback

horseback is a   Noun

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.

Synonyms: