horizontal bar vs exerciser

horizontal bar and exerciser both are nouns.

Word	Noun	Adjective	Verb	Adverb
horizontal bar	Yes	No	No	No
exerciser	Yes	No	No	No

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

horizontal bar: gymnastic apparatus consisting of a bar supported in a horizontal position by uprights at both ends
exerciser: sports equipment used in gymnastic exercises

Other hypernyms of horizontal bar include gymnastic apparatus.

horizontal bar (noun)	exerciser (noun)
gymnastic apparatus consisting of a bar supported in a horizontal position by uprights at both ends	sports equipment used in gymnastic exercises