quirky vs offbeat

quirky is not a noun while offbeat is a noun.

Word	Noun	Adjective	Verb	Adverb
quirky	No	Yes	No	No
offbeat	Yes	Yes	No	No

As adjectives, quirky and offbeat are synonyms defined as:

Other synonyms of quirky include far-out, kinky, way-out.

quirky (noun)	offbeat (noun)
	an unaccented beat (especially the last beat of a measure)

quirky (adjective)	offbeat (adjective)
(informal) strikingly unconventional	(informal) strikingly unconventional