noun

1. An unaccented beat at the start of a musical phrase.

   “The conductor said: I give you three beats for nothing and then you come in on the upbeat.”

Synonyms: anacrusis, anticipatory, anticipatory note, pickup, unaccented beat

adjective

1. Having a fast pace, tempo, or beat.

   “The notes are easy, but it's an upbeat tune and should be played fairly quickly.”

2. Having a positive, lively, or perky tone, attitude, etc.

   “He sounded upbeat when I talked to him.”