middleweight vs prizefighter

middleweight and prizefighter both are nouns.

Word	Noun	Adjective	Verb	Adverb
middleweight	Yes	No	No	No
prizefighter	Yes	No	No	No

As nouns, prizefighter is a hypernym of middleweight; that is, prizefighter is a word with a broader meaning than middleweight:

Other hypernyms of middleweight include gladiator.

middleweight (noun)	prizefighter (noun)
a professional boxer who weighs between 155 and 160 pounds	a professional boxer
a wrestler who weighs 172-192 pounds
an amateur boxer who weighs no more than 165 pounds