it's L33T lingo...
back in the day when script kiddie hacker wannabee's were DDOS'n the world and thought they were kewl.
L33T: For example, the term "leet" itself is often written "l33t" or "1337". Leet (or 1337, l33t, l33+, etc, derived from the word "Elite") is a linguistic phenomenon associated with the underground culture centered on telecommunications,...For the purposes of this text, leet is defined as the corruption or modification of written text.
DDOS : A Distributed Denial of service attack (DDoS) involves multiple compromised systems flooding the bandwidth or resources of a targeted system usually a web server(s). These systems are compromised by attackers using a variety of methods.
Translation, it's cultural slang, from when teenage hackers 'd systems so they couldn't be used, and thought they were kool for interupting commerce.