'Horseback' definitions:

Definition of 'horseback'

From: WordNet
adverb
On the back of a horse; "he rode horseback to town"; "managed to escape ahorse"; "policeman patrolled the streets ahorseback" [syn: horseback, ahorse, ahorseback]
noun
The back of a horse
noun
A narrow ridge of hills [syn: hogback, horseback]

Definition of 'Horseback'

From: GCIDE
  • Horseback \Horse"back`\, n.
  • 1. The back of a horse. [1913 Webster]
  • 2. An extended ridge of sand, gravel, and boulders, in a half-stratified condition. --Agassiz. [1913 Webster]
  • On horseback, on the back of a horse; mounted or riding on a horse or horses; in the saddle. [1913 Webster]
  • The long journey was to be performed on horseback. --Prescott. [1913 Webster]

Synonyms of 'horseback'

From: Moby Thesaurus