boyfriend vs adult male

boyfriend and adult male both are nouns.

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

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

Other hypernyms of boyfriend include lover, man.

boyfriend (noun)	adult male (noun)
a man who is the lover of a man or woman	an adult person who is male (as opposed to a woman)