to be in an upright position on your feet; to get yourself into an upright position on your feet

I've been standing up all day and I'm really tired. 我站了一天，现在很疲倦。

It was customary then for children to stand up when the teacher came into the classroom. 那时候的习俗是当老师进入课堂时，孩子们必须起立。

If an idea or some information stands up, it is proved to be true or correct.

Their evidence will never stand up in court. 他们的证据在法庭上根本站不住脚。

Their argument won't stand up to detailed criticism (= when it is studied critically). 他们的论点经不起仔细推敲。

to intentionally fail to meet someone when you said you would, especially someone you were starting to have a romantic relationship with

I don't know if I've been stood up or if she's just late - I'll wait another half hour. 我不知道她是故意放我的鸽子，还是只是迟到了——我会再等半个小时。