The title given to a gamer with skills almost that of godlike that people assume one is hacking. To recieve this is title is the greatest honour of a gamer.
A '1337' way of expressing one's feelings about an unfavourable situation - most frequently used when someone is beaten, outdone or likewise. In full, it means 'Oh My God, you have used some sort of cheating mechanism to beat me'.
Originates from claiming that a computer gamer is winning by using a hack (see hax).