Mortal Pwnage is the sound that emerges from a victors mouth after annhiliating one's opponent on a FPS game.
You've just creamed your friend sooooo harshly and humiliated him on Halo that you turn round and scream "Morrrrrrrrtalllllllll Pwwwwwnage!" whilst flipping him the finger.
by Gavyn Hughes June 5, 2005