stewardess vs adult female

stewardess and adult female both are nouns.

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

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

Other hypernyms of stewardess include flight attendant, steward, woman.

stewardess (noun)	adult female (noun)
a woman steward on an airplane	an adult female person (as opposed to a man)