To put your hand in a fist and punch someone (or something) so hard it ends up looking like a biscuit
To punch something so hard that your hand feels like a biscuit afterwards
If she says one more thing about me, I'll biscuit fist her so hard.
I got mad once and biscuit fisted my wall.... there's a major hole in it now.
After I biscuit fisted John, his face was so messed up he had to go to the hospital.
A biscuit fist is when you take your fist like a club and punch the temple area of someones head.
Joe biscuit fisted Steve after they got into a fight.