I jumped back and fell on my ass.

我往后一跳，摔了个屁股墩。

《柯林斯英汉双解大词典》

You have been on my ass ever since New York.

在纽约的时候你就已经让我不胜其烦了。

youdao

I got up to get off the train and landed on my ass.

当我站起来准备下地铁的时候，我摔倒了。

youdao

Forgot to put on my pants and fell flat on my ass.

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"This year, I'm going to put my ass on the line and tell you he's going to win the gold medal, " Siegel said.

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