fall in upon   (TTS發音)

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學。

2. visit by chance順便訪問

    You are welcome to fall in upon us at any time you like. 你什麼時候來玩，我們都歡迎。