The greek version of laugh out loud. Originates from the fact that many greekwords end in -os.
You: Hey man, I made some tzatziki and put some mint and dill in it!
Your greekfriend: That's not how you make tzatziki, no mint, no dill!
You: LOLOSS!
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.