an extension of the word ROFL. Typically used either to emphasize how much someone ROFL'd or in a cheesy satirical way making fun of people who use such retardedwords.
Dude: So I'm at this party and Jason was wasted and he fell through the bathroom door with his pants down!
Guy: ROFL!!
Dude: Then, to make it worse, he shit his pants on the way home in Rachel's car!
Guy: ROFLGANGER!
Dude: Guy, you are so retarded. Why do I talk to you?
n. software that is no longer sold or supported by the original publisher / developer, often found as free downloads on the internet because it cannot be obtained elsewhere. Not legal, but often seen as morally acceptable because the company that made it is no longer selling the title, nor releasing it as freeware, therefore abandonware is "keeping the gamealive", so to speak.
Doom II is not abandonware because idstill sells it, while The Incredible Machine is not sold, therefore is abandonware.