offbeat vs upbeat

offbeat and upbeat both are nouns.

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

As nouns, offbeat and upbeat are synonyms defined as:

offbeat and upbeat: an unaccented beat (especially the last beat of a measure)

offbeat (noun)	upbeat (noun)
an unaccented beat (especially the last beat of a measure)	an unaccented beat (especially the last beat of a measure)
	a contented state of being happy and healthy and prosperous

offbeat (adjective)	upbeat (adjective)
(informal) strikingly unconventional	pleasantly (even unrealistically) optimistic