Originally Posted by arcane93

Generally, what that means is that the game disc was reproduced without the copy protection measures (game discs are easy to reproduce; the copy protection, not so much). A normal, non-modded system will see that there is no copy protection on the disc and will refuse to play the game, whereas a "bootlegged"/modded system will skip over the copy protection check and will play the game as normal. So yeah, it definitely does exist.

Unfortunately, when you're just buying discs up in bulk like you do, you're likely to get some of those, and sometimes it can be hard to recognize them just by looking at them. It's another one of the downfalls of buying that way.