cover girl vs pin-up

cover girl and pin-up both are nouns.

Word	Noun	Adjective	Verb	Adverb
cover girl	Yes	No	No	No
pin-up	Yes	No	No	No

As nouns, cover girl and pin-up are synonyms defined as:

cover girl and pin-up: a very pretty girl who works as a photographer's model

Other synonyms of cover girl include lovely.

cover girl (noun)	pin-up (noun)
a very pretty girl who works as a photographer's model	a very pretty girl who works as a photographer's model