The Collaborative International Dictionary of English v.0.48:

Solfeggio \Sol*feg"gio\, n.[It., fr. solfa the gamut.] (Mus.)
   The system of arranging the scale by the names do, re, mi,
   fa, sol, la, si, by which singing is taught; a singing
   exercise upon these syllables.
   [1913 Webster]

WordNet (r) 3.0 (2006):

solfeggio
    n 1: singing using solfa syllables to denote the notes of the
         scale of C major [syn: solmization, solfege,
         solfeggio]
    2: a voice exercise; singing scales or runs to the same syllable
       [syn: solfege, solfeggio]