Source : Webster's Revised Unabridged Dictionary (1913)

Arpeggio \Ar*peg"gio\, n. [It., fr. arpeggiare to play on the
   harp, fr. arpa harp.] (Mus.)
   The production of the tones of a chord in rapid succession,
   as in playing the harp, and not simultaneously; a strain thus
   played.

Source : WordNet®

arpeggio
     n : a chord whose notes are played in rapid succession rather
         than simultaneously