turn on a dime要是直译就是在一个十分硬币上打转。dime是个一丁点儿大小的银圆，所以turn on a dime一定是形容在极小极小的地方打转。换句话说是活动非常灵巧，在极小的空间中转弯，事情很快会有变化。

【例句】
You know the car is ten years old and one of these days I'll have to spend the money to buy a new one. But there's one thing I love about it, the way it handles - it can really turn on a dime, just like one of those expensive sports cars.
你知道我那辆车已经开了十年了，近期内我不得不花钱去买辆新的。但是我喜欢这辆车开起来运转自如。它确实非常灵巧，就象那些价值昂贵的赛车那样。

You shouldn't worry about money, situations can turn on a dime, just be patient.
你不应该担心钱。情况变化无常，要有耐心。