To win, or more specificly to win by a large margin. Common usage among internet gamers.
I 0wn j00!
1) To win a game or competition (against another person or team) decisively.
2) To gain or exploit administrative access to a remote computer, esp. when such access is illicit.
3) (less common) To exhibit extreme goodness, mastery, skill, etc.; to command respect and admiration.
1. "Dude, you just ate five rockets - gamer3003 0wnz j00!" (note the 'z' ending and altered spelling of 'you')
2. The main webpage of xyz.com was defaced yesterday, someone probably 0wned their web server...
3. The Urban Dictionary 0wnz, man - you can look up ANYthing!