Shotgun is a firearm that fires shot over short ranges. It is usually fired from the shoulder. Shot guns come in a wide variety of forms – from very small to massive guns. Ammunition for shot guns is referred to as shotgun shells shotshells, or just shells. Generally shotguns are used against small and fast moving objects. In the US and Canada, shotguns are widely used as a heavy weapon by police forces.Shot guns are also reffered to as scatter guns or pepper guns.
The term 'shotgun' means “a weapon designed or redesigned, made or remade, and intended to be fired from the shoulder and designed or redesigned and made or remade to use the energy of the explosive in a fixed shotgun shell to fire through a smooth bore either a number of projectiles (ball shot) or a single projectile for each pull of the trigger, and shall include any such weapon which may be readily restored to fire a fixed shotgun shell.” (26 USCS § 5845)