desu
It a meme on 4-chan to let newfag's release the immense faggity inside them. It can also be used by trolls and other such assholes for the same reason. It is often spammed in ridiculous amount and pisses most people off. It has NOTHING to do with pwning or awesomeness.
4chan user- DeMotivational poster thread GO!!
Newfag-desudesudesudesudesudesudesudeusdeusdesudsuedusedesudesudesudesudesudesudesudesudesu... and so on
4chan user-shut the fuck up
Newfag-desudesudesudesudesudesudesudeusdeusdesudsuedusedesudesudesudesudesudesudesudesudesu... and so on
4chan user-shut the fuck up