Line of scrimmage

[Agnes]

Line of scrimmage in American Football. Is an imaginary line that exists once the ball has been placed on the field for offensive play. The imaginary line runs through the center of the ball and on either side across the width of the field. Players from both teams are not allowed to cross the line until the ball is snapped by the center.

[Dianne]

in American football, the line on which the ball is positioned at the beginning of play (= a period of action)