Typically an individual whom excessively shouts at a friend who is trying to enjoy a game. Feeling that if the person isn't doing well in the game for lack of concentration. To the surroundings in the game, that by shouting in the person's ear on how to do it, the white noise being yelled at in the background will somehow improve concentration. Sometimes this can be beneficial while at other times you want to shove the controller down their throat and hang them from the ceiling with the cord.
"Dude you're not doing it right! Don't use that gun, use the other!"
"You better shut the hell up with the back seat gaming it's getting on my nerves..."