A juke is a move in most forms of American football used to evade a tackler by deception, and thus without need of a stiff arm. It can also be called sidestepping.
A typical juke involves a ball-carrier faking as if he will run one way, then planting his foot and running the opposite. When this is done against the flow of play, it is called a cutback.
One variation on the common juke is a spin move.