adult female vs adult

adult female and adult both are nouns.

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

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

Other hypernyms of adult female include grownup, female, female person.

adult female (noun)	adult (noun)
an adult female person (as opposed to a man)	any mature animal
	a fully developed person from maturity onward

adult female (adjective)	adult (adjective)
	(of animals) fully developed
	designed to arouse lust