like terminal velocity, the rate at which a person's bitching gets them bitch slapped.
A Person achieves their Terminal Bitchosity when the downward force of their bitching (Fb) equals the upward force of a fist coming at them (Ff). This causes the net bitching on the object to be zero, resulting in an acceleration of zero.
Did you see that? She called him pencil dick and he smacked her. She finally found terminal bitchosity.