OMG duh...1337...It's upside down backwards calculator speak for "LEEI"
Leet (written as 31337, 1337, and l33t), or Leetspeak, is a written argot used primarily on the Internet, which uses various combinations of alphanumerics to replace Latinate letters. The term itself is a degenerate form of the word "elite", and the usage it describes is a specialized form of shorthand. Initially, the word leet was used as an adjective, to primarily describe the behavior or accomplishments of others in the community. In that usage, Leet generally carries the same meaning when referring to either the game prowess or, in original usage, hacking expertise of another person. From adjective form its use then expanded to include use as an expletive in reaction to a demonstration of the former qualities. With the mass proliferation of Internet use in the 1990s into the 21st century, Leet has since become a part of Internet culture and slang. Leet may also be considered a substitution cipher, albeit with much variation from user to user.