IPA: /ˈreɪsˌhɔːrs/
KK: /ˈreɪsˌhɔrs/
A horse that is specifically bred and trained to compete in races.
The racehorse won the championship after a thrilling competition.
Racehorse → It is formed from "race" (from Old French *racier*, meaning to run) and "horse" (from Old English *hors*, meaning a large domesticated animal used for riding). The word "racehorse" refers to a horse that is specifically bred and trained for racing.
Think of a horse that is 'running' ('race') — that's why a racehorse is a horse trained for racing.