Flash hider
A flash suppressor is a device attached to a rifle to reduce the brilliant muzzle flash which occurs upon firing. Muzzle flash is especially visible at night, and makes it easy to see the location of the shooter. It is caused by incandescence of the expanding gases produced by burning gunpowder.
Flash suppressors work by allowing the propellant gases to cool before dissipating. It is commonly thought that they are used on military rifles to reduce visibility to the enemy, but the size of a device necessary to hide the muzzle flash from an enemy during the night would be prohibitive. Flash suppressors are designed to hide the muzzle flash from the shooter to preserve his or her night vision, usually by directing the incandescent gasses downward, away from the line of sight of the shooter. Military forces engaging in night combat are still quite visible, and must move quickly after firing to avoid return fire.
Muzzle flash can also be controlled by using cartridges with a faster-burning powder, so that the propellant gases will already have begun to cool by the time they exit the barrel. Faster-burning powder, however, produces less projectile velocity, which reduces both the accuracy and lethality of the weapon.
Infrequently the term also is used referring to technologies that allow web browsers to selectively suppress Macromedia Flash animations, i.e. Flash Click To View for Mozilla.