pacemaker vs race horse

pacemaker and race horse both are nouns.

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

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

Other hypernyms of pacemaker include bangtail, racehorse.

pacemaker (noun)	race horse (noun)
a horse used to set the pace in racing	a horse bred for racing
an implanted electronic device that takes over the function of the natural cardiac pacemaker
a specialized bit of heart tissue that controls the heartbeat
a leading instance in its field