say it: HAWRS-bak
horseback is a noun and adverb meaning "the back of a horse". It carries 3 recorded senses.
on the back of a horse
“he rode horseback to town”
“managed to escape ahorse”
“policeman patrolled the streets ahorseback”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for horseback come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.