Pwn is a slang term that implies domination or humiliation of a rival, used primarily in the Internet gaming culture to taunt an opponent that has just been soundly defeated. Past tense is sometimes spelled pwnt (pronounced with a t sound) or pwned (with the standard d sound). Examples include "pwnage" or "you just got pwned". It can also be used, especially by non-gamers, in the context of getting "pwned" by The Man. It is also a variant of the expression "you got served" which is also used to describe someone or something that has either lost badly or been humiliated (or possibly both).
In Internet security jargon, to "pwn" means "to compromise" or "to control", specifically another computer (server or PC), web site, gateway device, or application; it is synonymous with one of the definitions of hacking. An outside party who has "owned" or "pwned" a system has obtained unauthorized administrative control of the system