look up any word, like pussy:
 
1.
Cool way of saying "for sure"... even cooler than "fa sho" or "fa shizzle".
Yo, you tryna' come to Applebee's with us?"
-Fo' shillz."

or...

"Yo, did you fuck that bitch last night?"
-"Fo' shillz."
by Boner_Boy June 30, 2011