In sports betting, a back door cover occurs when the team you wagered on covers the spread in the last minutes of the game. Often times this happens when the actual game is a blow out, yet the spread or line of the game is still at play.
The Giants kicked a late field goal to give me a back door cover. They lost by 10, but covered the 12 point spread.
by Milt Deezy April 27, 2007