What it is

A stiff-arm is a move where the ball carrier extends his free arm and pushes against a tackler’s helmet or shoulder to keep him away.

In a game

It lets a runner break free from a tackle without losing speed. A strong stiff-arm can also push a defender to the ground.

More detail

Runners use the arm opposite the defender and keep the ball tucked in the other. Some runners are famous for it, because a good stiff-arm turns a certain tackle into extra yards.