cross one's fingers

cross one's fingers，即把中指叠在食指上，两指交叉(crossed)成X状，这样就像一个十字架，可以辟邪、祈福。现在，人们常常用cross one's fingers，keep one's fingers crossed来说祈求好运。

to hope that things will happen in the way that you want them to

祈求好运

例：

We're keeping our fingers crossed that the weather stays nice.

我们企求天公作美，希望能一直保持这么好的天气。