Someone (usually stereotypical minorities, white trash, or insecure kids under the age of 14) who plays an online videogame like Halo, Call of Duty, or even World of Warcraft, but takes the game to an ultimate level of epic failure and faggotry. MLG fags usually think they are the best players, however this is not the case as any moderately skilled or intelligent player can beat them in a legitimate game. 99% of the time MLG fags like to use gang up tactics, power weapons, rushing, boosting, network manipulation, ingame combat exploits, or just trash talking the other team into leaving the game. Approximately 1% of the time they actually have skill, but with the drawback of having absolutely no life. It is also important to note that many MLG fags don't go outside, as they would probably get shot if they walked out into their shitty ghetto neighborhood.
MLG fags tend to have names like the following: mLgLoPeZz, Xxmlglilwayne69xX, mLG1sH0t1kIL, and mlgsmokew33d420420,