D defs.my
Entry 2 senses Webster, 1913

Horseback

/hôr'-sbăkˌ/ · Horse·back · IPA /ˈhɔɹsˌbæk/
01 n. The back of a horse.
  1. 1.
    The back of a horse.
  2. 2.
    An extended ridge of sand, gravel, and boulders, in a half-stratified condition.
    “The long journey was to be performed on horseback.” Prescott.