trotter vs racehorse

trotter and racehorse both are nouns.

Word	Noun	Adjective	Verb	Adverb
trotter	Yes	No	No	No
racehorse	Yes	No	No	No

As nouns, racehorse is a hypernym of trotter; that is, racehorse is a word with a broader meaning than trotter:

trotter: a horse trained to trot; especially a horse trained for harness racing
racehorse: a horse bred for racing

Other hypernyms of trotter include bangtail, race horse.

trotter (noun)	racehorse (noun)
a horse trained to trot; especially a horse trained for harness racing	a horse bred for racing
foot of a pig or sheep especially one used as food