A pronub is a nub who utilizes cheats to help him with his lack of playing skills. There are generally two groups of pronubs. Group one are jerks who use there hacks to pwn other people. Group two are people who use there skills (hacks) to have as much fun as possible with friends and other players. A regular video game hacker is not considered a pronub unless he has very little skill without the help of hacks.
Even though the player was a nub at the game his hacks helped convert him into a pronub.