Personal defense weapon
The United States Department of Homeland Security defines a personal defense weapon as an M4 carbine (or a Colt AR-15 civilian semi-automatic rifle). Some governments' definition of PDWs includes handguns. An example is the Czech Republic. It has proposed a constitutional amendment which would allow its citizens to own and keep PDWs as a way to discourage terrorists. Regardless, a PDW is usually agreed upon as being somewhere between a submachine gun and an assault rifle.