do a U-turn

1. Literally, to make a sudden 180-degree turn, such that one or one's vehicle is quickly facing or moving in the opposite direction. Once I realized I was going the wrong way, I had to do a U-turn at the next light. When I saw Mary in the hallway, I did a U-turn and went back the way I came. I was going to go to the park, but when I saw those dark clouds roll in, I did a U-turn and headed back home.

2. By extension, to make any sudden and drastic reversal, as of opinion, policy, intention, fortune, trend, etc. After a huge public outcry about the controversial program, the president quickly did a U-turn and announced that he would not support the plan. The tech giant typically has unyielding success, but they did a major U-turn with the disastrous unveiling of their latest gadget. A: "Can you believe that Sam quit his job at the firm?" B: "No, he really did a U-turn on being a paralegal!"