coxcomb vs fashion plate

coxcomb and fashion plate both are nouns.

Word	Noun	Adjective	Verb	Adverb
coxcomb	Yes	No	No	No
fashion plate	Yes	No	No	No

As nouns, fashion plate is a hypernym of coxcomb; that is, fashion plate is a word with a broader meaning than coxcomb:

coxcomb: a conceited dandy who is overly impressed by his own accomplishments
fashion plate: a man who is much concerned with his dress and appearance

Other hypernyms of coxcomb include beau, clotheshorse, dandy, dude, fop, gallant, sheik, swell.

coxcomb (noun)	fashion plate (noun)
the fleshy red crest on the head of the domestic fowl and other gallinaceous birds	a plate illustrating the latest fashion in dress
a cap worn by court jesters; adorned with a strip of red	a man who is much concerned with his dress and appearance
a conceited dandy who is overly impressed by his own accomplishments