barman vs adult male

barman and adult male both are nouns.

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

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

Other hypernyms of barman include barkeep, barkeeper, bartender, mixologist, man.

barman (noun)	adult male (noun)
a male employee who mixes and serves alcoholic drinks at a bar	an adult person who is male (as opposed to a woman)