Source : Webster's Revised Unabridged Dictionary (1913)

Acciaccatura \Ac*ciac`ca*tu"ra\, n. [It., from acciaccare to
   crush.] (Mus.)
   A short grace note, one semitone below the note to which it
   is prefixed; -- used especially in organ music. Now used as
   equivalent to the short appoggiatura.

Source : WordNet®

acciaccatura
     n : an embellishing note usually written in smaller size [syn: {grace
         note}, {appoggiatura}]
     [also: {acciaccature} (pl)]