washerwoman vs adult female

washerwoman and adult female both are nouns.

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

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

Other hypernyms of washerwoman include washer, woman.

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