Usualy used in online games when you completely destroysomeone with no hope of them doing any damage back.
Usualy when someone experianced beats someone much less experianced hands down. Or (for example in eve-online) a fleet of ships takes on one person who clearly has no hope of winning against them. IE they will be/have been Pewned.
A series of news flashes posted on PewDiePie’s YouTube account (but not hosted by himself), which is otherwise known as the most reliable and reputable news source to exist. PewNews covers topics ranging from YouTube drama to bad feminist video games. Previous episodes of PewNews have been hosted by Gloria Borger, Poppy Harlow, Poppy Gloria, Opsie Dopsie, etc..
A corruption of the word "Owned." This originated in an online game called Warcraft, where a map designer misspelled "owned." When the computer beat a player, it was supposed to say, so-and-so "has been owned."
Instead, it said, so-and-so "has been pwned."
It basically means "to own" or to be dominated by an opponent or situation, especially by some god-like or computer-like force.
"Man, I rock at my job, but I still got a bad evaluation. I was pwned."