On a firearm or other tools, a pistol grip is a distinctly protruded handle underneath the main mechanism, to be held by the user's hand at a more vertical (and thus more ergonomic) angle, similar to how one would hold a conventional pistol.[1]
In firearms, the pistol grip is located behind the trigger and generally held by the hand that operates the trigger. Rifles and shotguns without pistol grips are generally referred to as having "straight" or "upland" (shotguns only) style stocks. Some firearms, starting from a 1840s Belgian carbine,[2] and most automatic weapons in the 20th century (e. g., Chauchat MG, Thompson submachine gun, AK-47 assault rifle), have a second frontal pistol grip (or foregrip) on the firearm's fore-end to be used by the support hand for better stability in operation.
One of the reasons that pistol-style grips are so common in machinery is because it is possible to ergonomically position the operating controls for use with minimal hand movement. For example, on self-loading rifles such as the AR-15 and M16 rifle, the user's grip hand can manipulate the trigger and magazine release with only the index finger, while using the thumb to control the safety or selector switch, all without needing to remove the palm from the grip.