Having a fast beat (2-5)
(Other definitions for up-tempo that I've seen before include "Musically, played (increasingly) fast" , "Played with a fast beat" , "Quick, cheerful (piece of music)" , "(Of music) played at fast speed" , "Played or sung at a fast speed" .)
(Other definitions for uptempo that I've seen before include "quickly in play" , "Lively" , "Played with a fast beat" , "Musically, played (increasingly) fast" , "Played smartly" .)