mad money （女子出门赴约时）自备的零钱，备急用的钱

【例句】
She had some mad money.
她有一笔应急的钱.

Fortunately, she had her mad money in her pocket to pay for the cake, so it turned out all right.
还好她口袋里有一些应急用的现金可以付蛋糕钱，所以就没问题了。