Basically what the other bozos on urbandictionary said it was:
"Many people will argue that it started with the popular game Counter Strike, but X's def. is the most correct. According to "The Hacker Crackdown" by Bruce Sterling, it was an invented language used to confuse FBI and NSA sniffing programs during Operation Sundevil, when the government placed "wiretaps" on the Killer server to find hackers. Used extensively after the E911 document scandal and the theft of Korn 78 and other UNIX programs by AT&T. Google "Fry Guy", "Terminus", "Gail Thackery", "Acid Phreak" and "Phiber Optik" for more information. Discontinued among true hackers thanks to encryption engines and PGP keys."
HOWEVER it is something much much more.
It is also a Hamilcar album - 12 TeamSpeak "pranks" featuring members of Niggas in the Struggle (NITS) among others. For more information please visit www.creative-minds.org (check the MISC section)
Yo son, Hamilcar's album "l337" definatly is l337.