nonstarter vs race horse

nonstarter and race horse both are nouns.

Word	Noun	Adjective	Verb	Adverb
nonstarter	Yes	No	No	No
race horse	Yes	No	No	No

As nouns, race horse is a hypernym of nonstarter; that is, race horse is a word with a broader meaning than nonstarter:

nonstarter: a horse that fails to run in a race for which it has been entered
race horse: a horse bred for racing

Other hypernyms of nonstarter include bangtail, racehorse.

nonstarter (noun)	race horse (noun)
a horse that fails to run in a race for which it has been entered	a horse bred for racing
a person with a record of failing; someone who loses consistently