Source : Webster's Revised Unabridged Dictionary (1913)

Crescendo \Cres*cen"do\ (kr?s-s?n"d?; It. kr?-sh?n"d?), a. &
   adv. [It., from crescere to increase. See {Crescent}.] (Mus.)
   With a constantly increasing volume of voice; with gradually
   increasing strength and fullness of tone; -- a direction for
   the performance of music, indicated by the mark, or by
   writing the word on the score.

Crescendo \Cres*cen"do\, n. (Mus.)
   (a) A gradual increase in the strength and fullness of tone
       with which a passage is performed.
   (b) A passage to be performed with constantly increasing
       volume of tone.

Source : WordNet®

crescendo
     adj : gradually increasing in volume
     n : (music) a gradual increase in loudness
     v : grow louder; "The music crescendoes here" [ant: {decrescendo}]
     [also: {crescendi} (pl)]