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!