Source : Webster's Revised Unabridged Dictionary (1913)

Allegretto \Al`le*gret"to\, a. [It., dim. of allegro.] (Mus.)
   Quicker than andante, but not so quick as allegro. -- n. A
   movement in this time.

Source : WordNet®

allegretto
     adj : (of tempo) faster than allegro
     n : a quicker tempo than andante but not as fast as allegro
     adv : in a moderately quick tempo; "play this more allegretto"