UPBEAT
cheerful, pollyannaish, upbeat
(adjective) pleasantly (even unrealistically) optimistic
upbeat, offbeat
(noun) an unaccented beat (especially the last beat of a measure)
wellbeing, well-being, welfare, upbeat, eudaemonia, eudaimonia
(noun) a contented state of being happy and healthy and prosperous; “the town was finally on the upbeat after our recent troubles”
Source: WordNet® 3.1
Etymology
Adjective
upbeat (comparative more upbeat, superlative most upbeat)
Having a fast pace, tempo, or beat.
Having a positive, lively, or perky tone, attitude, etc.
Antonyms
• (optimistic): downbeat
Noun
upbeat (plural upbeats)
An unaccented beat at the start of a musical phrase.
Synonyms
• unaccented beat
• anticipatory note, anticipatory
• unstressed note, unstressed
• anacrusis
• pickup
Anagrams
• beat up, beat-up
Source: Wiktionary