The Collaborative International Dictionary of English v.0.48:

bel canto \bel canto\ (b[e^]l k[aum]n"t[-o]), n. [It., beautiful
   singing.] (Music)
   a cantabile style of operatic singing characterized by purity
   and evenness of tone, and a precise but brilliant vocal
   technique displaying ease and agility.
   [PJC]

WordNet (r) 3.0 (2006):

bel canto
    n 1: a style of operatic singing

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "bel canto":
   bravura, choral singing, coloratura, croon, crooning, folk singing,
   hum, humming, intonation, lyricism, operatic singing, scat,
   scat singing, singing, sol-fa, sol-fa exercise, solfeggio,
   solmization, song, tonic sol-fa, vocal music, vocalization,
   warbling, yodel, yodeling