2: A substitute for "Unbelievable", "Amazing", "Astounding", and other remarks of extreme approval; Usually referring to music.
3: World Of Warcraft-specific slang for the Shadow Priest class.
4: A term for when a man ejaculates a large quantity of semen on a woman's face, thus giving it the appearance of "melting"
2) The band Joe had playing on the stereo was facemeltingly good.
3) I was grinding my paladin up some levels when this jerk obliterated me with his facemelter.
4) The facemelter, as seen in countless pornographic videos and pictures.