Source : Webster's Revised Unabridged Dictionary (1913)

Viola \Vi"o*la\, n. [It. See {Viol}.] (Mus.)
   An instrument in form and use resembling the violin, but
   larger, and a fifth lower in compass.

   {Viola da braccio} [It., viol for the arm], the tenor viol,
      or viola, a fifth lower than the violin. Its part is
      written in the alto clef, hence it is sometimes called the
      {alto}.

   {Viola da gamba} [It., viol for the leg], an instrument
      resembling the viola, but larger, and held between the
      knees. It is now rarely used.

   {Viola da spalla} [It., viol for the shoulder], an instrument
      formerly used, resembling the viola, and intermediate in
      size between the viola and the viola da gamba.

   {Viola di amore} [It., viol of love: cf. F. viole d'amour], a
      viol, larger than the viola, having catgut strings upon,
      and brass or steel wires under, the keyboard. These,
      sounding sympathetically with the strings, yield a
      peculiarly soft and silvery sound. It is now seldom used.

Source : WordNet®

viola da braccio
     n : a member of the viol family with approximately the range of
         a viola