"horseback" in the noun sense
the back of a horse
2. hogback, horseback
a narrow ridge of hills
"horseback" in the adverb sense
1. horseback, ahorse, ahorseback
on the back of a horse
"he rode horseback to town"
"managed to escape ahorse"
"policeman patrolled the streets ahorseback"
Source: WordNet® (An amazing lexical database of English)
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