A male figure whose presence has an adverse effect on another mans relationship with their girlfriend
"yo that bitches ex-boyfriend is totally fucking with Anthony's head, hes causing some serious fkb effect
by greg johnson the third October 30, 2007

"Bro, you got chili on your shirt."
"Yeah, it's going to leave a vicious Fat Kid Badge "FKB", good thing I carry a tide pen."
"Yeah, it's going to leave a vicious Fat Kid Badge "FKB", good thing I carry a tide pen."
by Caveman4hire January 18, 2019

by Joel de Fisher November 29, 2023
