old-hat vs passe

old-hat and passe both are adjectives.

Word	Noun	Adjective	Verb	Adverb
old-hat	No	Yes	No	No
passe	No	Yes	No	No

As adjectives, old-hat and passe are synonyms defined as:

Other synonyms of old-hat include antique, demode, ex, old-fashioned, outmoded, passee.

old-hat (adjective)	passe (adjective)
out of fashion	out of fashion
repeated too often; overfamiliar through overuse