Source : Webster's Revised Unabridged Dictionary (1913)

Allegro \Al*le"gro\, a. [It., merry, gay, fr. L. alacer lively.
   Cf. {Aleger}.] (Mus.)
   Brisk, lively. -- n. An allegro movement; a quick, sprightly
   strain or piece.

Source : WordNet®

allegro
     adj : (of tempo) fast

allegro
     n 1: a brisk and lively tempo
     2: a musical composition or passage performed quickly in a
        brisk lively manner
     adv : in a quick and lively tempo; "play this section allegro"

Source : Free On-Line Dictionary of Computing

Allegro
     
         The code name for the major {Mac OS}
        release due in mid-1998.
     
       
     {(http://devworld.apple.com/mkt/informed/appledirections/mar97/roadmap.html)}.
     
        (1997-10-15)