washwoman vs adult female

washwoman and adult female both are nouns.

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

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

Other hypernyms of washwoman include washer, woman.

washwoman (noun)	adult female (noun)
a working woman who takes in washing	an adult female person (as opposed to a man)