The guards, he said, would punch them for no reason.

他说看守人员们会无缘无故地用拳头打他们。

《柯林斯英汉双解大词典》

His wife was troubled about being shouted at for no reason.

他的妻子因无缘无故被人大骂而烦恼。

youdao

I often fell down for no reason.

我经常无缘无故地摔倒。

youdao

He seemed to kill for no reason, and with no emotion, as if taking someone's life meant nothing.

VOA: special.2009.12.13

swinging a baseball bat at me on the subway train for no reason, except that he's crazy.

他在地铁上无端地朝我挥动棒球拍，没有理由，除非他疯了。

向哥伦布学习 - SpeakingMax英语口语达人

So I wrote my dissertation on Byron as a result of that-- nothing complicated, no deep reason for doing these things.

所以我论文写的就是关于拜伦的-,没有太多的考虑，就是因为我喜欢。

耶鲁公开课 - 文学理论导论课程节选

As an illustration consider someone punching you in the nose on the bus for no reason.

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In any case, my mother did, at some point, open the door, for no reason.

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Montezemolo and Della Valle talk all the time, often for no reason at all.

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