on the spur of the moment

一时冲动之下, 当即

详细释义：

随兴所至; 一时冲动

He bought the car on the spur of the moment.

他临时起意买了一辆车。

He asked her to marry him on the spur of the moment.

他一时冲动之下向她求婚了。

I just took the bus on the spur of the moment.

我是一时兴起才跳上公共汽车的。