Beyond simple a simple pwn, "wtfpwn" means to pwn someone in a quick and decisive manner, such that they don't know what hit them and/or have little chance to react before dying.
My lvl 60 rogue stealth'ed and wtfpwn'ed those gray noobs.
By Cindi
Wtfpwn
To wtf pwn, is to completely and utterly destroy something in style, commonly used by "wtf 1337 cnuts" like fw.
Combination of WTF (What the fuck) and PWNS ('owns' in the sense of 'defeats', see: PWN). Used to describe a total victory over someone who didn't even stand a chance.
