When you see something you can never unsee, regardless of how much bleach and hallucinogenics you use to try to forget it.
I'm a parent who usually doesn't nose into my kid's business, but, one day, I opened up my son's laptop out of idle curiosity. His browser was open, and was currently on the Google Images page of "Zoophilia." It is three hours later, I have downed THREE BOTTLES OF SNAKE VENOM, and my eyes are bleeding.
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.