In Football, a false start is a penalty that is called on the offensive team when an offensive player begins moving (like the ball has been snapped) before the ball is snapped. A false start is also called if movement by an offensive player causes a defensive player to cross the line of scrimmage. This penalty results in a 5 yard loss for the offense.
Illegal movement of the ball, such as the center swaying the ball in a harsh motion, that causes a defensive player to move across the line of scrimmage is also a false start against the offense. Also, any forward motion towards the line of scrimmage is a false start.