Definition
Used to emphasize that something will never happen.
指某事绝不可能发生。
He promised to give us a raise after the company layoffs, which will happen when hell freezes over.
他承诺在公司裁员后给我们加薪，这永远不可能发生。
You say he'll be on time? That will happen when hell freezes over!
你说他会准时？那永远不可能发生！
I will never forgive him, that'll happen when hell freezes over.
我永远不会原谅他，那永远不可能发生。