bass viol

from the GNU version of the Collaborative International Dictionary of English.

• (Mus.) A stringed instrument of the viol family, used for playing bass. See 3d bass, n., and violoncello.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A fretted, bowed, stringed musical instrument from the viola da gamba family. It occupies the bass range and is the lowest instrument in the family. Similar to (but smaller than) a cello.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun viol that is the bass member of the viol family with approximately the range of the cello
• noun largest and lowest member of the violin family