pistol grip

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The grip of a pistol, shaped to fit the hand.
• noun A similar grip sometimes used on a submachine gun or other firearm.
• noun A grip used on certain tools, such as a saw, shaped to fit the hand.

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

• noun The grip by which a pistol is held in the hand
• noun A similarly shaped grip on any of several firearms, swords and tools

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

• noun a handle (as of a gun or saw) shaped like the butt of a pistol