An online or cell phone IM language now used mostly by non-adults, but having richer roots in the 1980's programming culture. Shares many memes with "ubonics", a discredited movement from before most users of "leet" were even born, celebrating ignorance and improper use of English. Much popular "leet" phraseology is simply glorified typos. Of course, teens and pre-teens have every right to a private code, this is part of the human experience. However, most people will out-grow "leet", except true social retards. Anyone over 20 using "leet" is suspect.
Exception: IM shorthand, such as "lmao".
("shorthand" is a word from the dark ages when people actually transcribed oral enouncications with pen and paper.)
1. I'm so leet dat I can IM without anybody knowing what the h311 I is sayizzing.
2. I is an ignorant crack-a-lacking moron.