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In sports, the opposite of "win and in"; describes a team's situation entering a game in which if the don't come out victorious, they are eliminated from postseason (the diffuse element is derived from the fact that the players on the team will go their separate ways at the conclusion of the season).
Man, if the Giants don't win this week, they can't make the playoffs.

Yeah dude, it's 'lose and diffuse' this week.
by T. Coughlin December 22, 2010