old-hat vs demode

old-hat and demode both are adjectives.

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

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

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

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