A bullet is a soli projectile propelled by a firearm or air gun and is normally made from metal (usually lead). A bullet does not contain explosives, but damages the intended target by tissue disruption and impact. The word "bullet" is sometimes erroneously used to refer to a cartridge, which is the combination of bullet, casing (case or shell), gunpowder and primer. See ammunition. The Oxford English Dictionary definition of a bullet is "a projectile of lead ... for firing from a rifle, revolver etc." However, bullets for air guns are not part of a cartridge.