AFB stands for "Away From Brain".
A typically AFB person is a person who acts just plainly brainlessly..AFB at first derived from the expression "afk", but "afb" stood firstly for a person , who wasn't afk, but acted just as retardedly as if he/she would've been it.
The AFB expression is used by 1337 speakers, who applies their 1337 speaking abilities to their everyday 1337'ish lifes.
T4RZ4N - Huååmfg!1!1! That oldz0id womanl0id is totally AFB't0id!!
PH1R3 - Like yeah? TOTALLY!