horse vs exerciser

horse and exerciser both are nouns.

Word	Noun	Adjective	Verb	Adverb
horse	Yes	No	Yes	No
exerciser	Yes	No	No	No

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

Other hypernyms of horse include gymnastic apparatus.

horse (noun)	exerciser (noun)
solid-hoofed herbivorous quadruped domesticated since prehistoric times	sports equipment used in gymnastic exercises
a chessman shaped to resemble the head of a horse; can move two squares horizontally and one vertically (or vice versa)
a framework for holding wood that is being sawed
a padded gymnastic apparatus on legs
troops trained to fight on horseback

horse (verb)	exerciser (verb)
provide with a horse or horses