A term from Gears of War online PVP. To "two piece" someone, you either use a double melee attack, first one stunning them, then the second downing, or use a weapon combo, such as melee stun, then shotgun them out.
The name given to an action in a game inwhich a melee is followed by a shotgun shot. The melee stuns a player and centers the oponent on the screen making the following shot a kill.
this action is often reffered to as "cheap" or "lacking in skill"