old-hat vs antique

old-hat is not a noun while antique is a noun.

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

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

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

old-hat (noun)	antique (noun)
	any piece of furniture or decorative object or the like produced in a former period and valuable because of its beauty or rarity
	an elderly man

old-hat (adjective)	antique (adjective)
out of fashion	made in or typical of earlier times and valued for its age
repeated too often; overfamiliar through overuse	out of fashion
	belonging to or lasting from times long ago

old-hat (verb)	antique (verb)
	give an antique appearance to
	shop for antiques