A Halo 2 term. It is simply when you are at point blank range with your opponent and you blast him in the face with a shotgun. It gets his name from Nirvana lead singer Curt Cobain who blew his head off with a shot gun.
I was playing some noob yesterday, and he accually was pathetic enough to let me get him with a Reverse Cobain!
A bulgarian backfire is a Halo 2 term. It is when a player tried to stick another player with a plasma grenade from point blank range, and the plasma bounces off the player and sticks to the person who threw the grenade.
"D00d! Sum n00b stuk m3 wi7h a Bulgarian Backfire last night on Xb0x Live!!!!11!!!11 I wuz s00 pissx0r3d!!!111!!1!1