A term commonly used towards someone who is playing amazing, or doing things which may look like they are cheating, when in fact, in most cases, they are not. Also used a complement to good players labelling their skills as good enough to be considered cheating.

Cheating or hacking programs in online multiplayer games such as Counter-Strike. The cheater often has an aimbot, can see players through walls, uses neon colored player models, and has decreased recoil to name a few advantages.

A word translated into 1337speak.

Most commonly used as a congratulation to someone whom is doing extremely well in a game, usually by the opposition.

And explanation of the undesirable unexpected.

So much ownage you must cheat.

Gaining access to another computer through an exploit. Can also be used in a sarcastic or funny way.

so 1337 they pwn nubs in teh nubish dome so much everyone thinks they h4x.