fall in upon -用法

fall in upon

1. come upon unexpectedly意外遇到

I fell in upon of my old classmates on my way home.在我回家的路上我遇到了一位老同学。

2. visit by chance顺便访问

You are welcome to fall in upon us at any time you like．你什么时候来玩，我们都欢迎。