chapeau vs top hat

chapeau and top hat both are nouns.

Word	Noun	Adjective	Verb	Adverb
chapeau	Yes	No	No	No
top hat	Yes	No	No	No

As nouns, top hat is a hyponym of chapeau; that is, top hat is a word with a more specific, narrower meaning than chapeau:

chapeau: headdress that protects the head from bad weather; has shaped crown and usually a brim
top hat: a man's hat with a tall crown; usually covered with silk or with beaver fur

chapeau (noun)	top hat (noun)
headdress that protects the head from bad weather; has shaped crown and usually a brim	a man's hat with a tall crown; usually covered with silk or with beaver fur