Used to indicate that the person speaking is under duress. Therefore, it negates the rest of the statement. Useful for lying discreetly at a social gathering or party. Used by Jack Bauer in the TV show 24.
(At crowded party)
Ben: Hey man, you and I are best friends forever, right?
Me: Sure. You and I are best friends. I am in a flank two position.
Girl: But you told me that you loved me last night, baby.
Me: I know I said that, but I was in a flank two position!