Source : Webster's Revised Unabridged Dictionary (1913)

Violoncello \Vi`o*lon*cel"lo\ (?; 277), n. [It. violoncello,
   dim. of violone a bass viol. See {Violone}.] (Mus.)
   A stringed instrument of music; a bass viol of four strings,
   or a bass violin with long, large strings, giving sounds an
   octave lower than the viola, or tenor or alto violin.

Source : WordNet®

violoncello
     n : a large stringed instrument; seated player holds it upright
         while playing [syn: {cello}]