a sudden and complete change of policy by a government or by someone in authority . This word usually shows that you do not approve of someone who does this （政策的）180度转变，急剧变化（该词表示不赞同这样做的人）
do a U-turn The government was today accused of doing a U-turn after its decision not to raise petrol prices after all. 政府在决定不提高汽油价格后又作出了180度的大转变，因此今天受到指责。
2
an act of turning a vehicle in order to travel in the opposite direction （车辆的）U形转弯，180度转弯，掉头