1 definition by Kaiveran
A door-breaching shotgun manufactured as a custom part by Knight's Armament Company. Can be mounted under the barrel on a M4 or M16 assault rifle, like a M203 grenade launcher.
The Masterkey project was initiated during the 1980s to provide assault rifles with a potent built-in door breaching tool.
by Kaiveran October 05, 2008