to Kick Some Butt. Refers to the act of bailing to a LAN cafe and pwning some noobs at left 4 dead or dota.
A: I've had enough of this club - let's just bail home...
B: C'mon! The night's still young, let's just ksb (at Cityhunter)!
just like csb, it stands for kool story bro
P1: In West Philadelphia, born n raised in da playground is where i spent most of my days, chillin out, maxin,relaxin all cool n all, shootin some b-ball outside of school, when a couple of guys who were up to no good started makin trouble in my neighbourhood i got in one lil fight n my mum got scared n said u your movin with your antie and uncle in bell air...