A word meant to mean leet (elite) written in numbers, each number corresponding to a letter. Used by kids who just found the internet and think it's zeroday shit that hackers do. You're about 9 years late kids and it was never considered cool. Also used by little gaywads for passwords to things they consider important.
Gaywad: m4ng 3y3 537 my p455w0rd 70 3r337h4x0r n0b0dy wi11 b3 4bl3 70 h4x0r my c0d3z.