knock up against -用法

knock up against

meet by chance巧遇；偶然碰到

I knocked up against my former teacher in the town this morning．今天早上在城里我遇见了我从前的那位老师。

I didn't expect to knock up against so many difficulties when I started on this subject．我没有料到这项目一开始就遇上了这么多的困难。