The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]WordNet (r) 3.0 (2006):
acciaccatura n 1: an embellishing note usually written in smaller size [syn: grace note, appoggiatura, acciaccatura]