barmaid vs adult female

barmaid and adult female both are nouns.

Word	Noun	Adjective	Verb	Adverb
barmaid	Yes	No	No	No
adult female	Yes	No	No	No

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

Other hypernyms of barmaid include barkeep, barkeeper, bartender, mixologist, woman.

barmaid (noun)	adult female (noun)
a female bartender	an adult female person (as opposed to a man)