omae wa mou shindeiru お前はもう死んでいる

If you're in an anime community, you might have seen the following meme already: omae wa mou shindeiru, or omae wa mou shinderu, followed by someone saying nani?! So, in case you're wondering what the hell are these weebs memeing about, it's a line from the manga and anime Fist of the North Star, Hokuto no Ken 北斗の拳.

Here's the translation:

Manga: Fist of the North Star, Hokuto no Ken 北斗の拳 (Chapter 1, 心の叫びの巻)

• omae wa mou shinderu.........
  おまえはもう死んでる･････････
  You're already dead.
• nanii~~!?
  なにィ～～！？
  Whattt!?

Note that shinderu しんでる is a contraction of shinde-iru しんでいる, the te-iru form of shinu 死ぬ, "to die," which is why some people say omae wa mou shindeiru お前はもうしんでいる instead.

Also note that there are differences between the magazine version, the complete edition, and the anime version. So it's likely the phrase has appeared as both shinderu and shindeiru sometime, making both perfectly correct.