1. Phrase used when a n33b
(dumbass scrub n00bster) complains about playing bad and makes up all kinds of excuses!
2. When you don't like someone while playing a game and even though they aren't saying anything you just want them to shut the fuck up.
n00b: I wonder why i've been doing bad all day...
n00b: I really am cal-main guys...
: STFU NOOB, no one gives a shit!
1337 pwner: whU R joo?
n00bert: Hi, it's my first day playing this game, How are you?
1337 pwner: STFU b1tch, and STFD no one cares b1tch