n (soccer|hurling|Gaelic football) the boundary of the field that runs along its width at each end, and across the front of the goal.
n (American football) part of a vertical plane separating an end zone from the field of play when the ball is touched or is in player possession. The plane extends beyond the sidelines. A team’s goal line is that which it is defending.
n (ice hockey) the red line that runs across the rink and the front of the goal.