call an audible

1. In American football, to call out a different play at the line of scrimmage just before the ball is put into play, typically in response to some action taken by the opposing team. (An "audible" is a play changed in this manner.) The quarterback called an audible after seeing how the defense had lined up.

2. By extension, to change one's decision or course of action in response to changing or previously unforeseen factors. I planned to take that route, but there's too much traffic now. I think I have to call an audible and take the highway instead.