showboy vs adult male

showboy and adult male both are nouns.

Word	Noun	Adjective	Verb	Adverb
showboy	Yes	No	No	No
adult male	Yes	No	No	No

As nouns, adult male is a hypernym of showboy; that is, adult male is a word with a broader meaning than showboy:

Other hypernyms of showboy include dancer, professional dancer, terpsichorean, man.

showboy (noun)	adult male (noun)
a man who dances in a chorus line	an adult person who is male (as opposed to a woman)