top hat vs dress hat

top hat and dress hat both are nouns.

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

As nouns, top hat and dress hat are synonyms defined as:

top hat and dress hat: a man's hat with a tall crown; usually covered with silk or with beaver fur

Other synonyms of top hat include beaver, high hat, opera hat, silk hat, stovepipe, topper.

top hat (noun)	dress hat (noun)
a man's hat with a tall crown; usually covered with silk or with beaver fur	a man's hat with a tall crown; usually covered with silk or with beaver fur