Source : Webster's Revised Unabridged Dictionary (1913)

Vivace \Vi*va"ce\, a. & adv. [It.] (Mus.)
   Brisk; vivacious; with spirit; -- a direction to perform a
   passage in a brisk and lively manner.

Source : WordNet®

vivace
     adj : (of tempo) very fast and lively
     adv : lively, in music; "play this section vivace!"