My mom was really upset because he was accusing her of having an affair with another man.

我妈妈真的很难过，因为他指责她和另一个男人有暧昧关系。

《柯林斯英汉双解大词典》

If he caught me with another man, he'd kill us both.

如果他撞见我和其他男人在一起，他可能会把我两都杀了。

youdao

By the same token, his girlfriend married with another man.

由于同样原因，他的女朋友嫁给了另一个男人。

youdao

It is about a ruler who believes wrongly that his wife has been with another man.

VOA: special.2010.01.13

But Claudio wrongly accuses Hero of being with another man and refuses to marry her.

VOA: special.2010.01.06

If he had another man with him, he would not be in any danger now.

VOA: special.2010.05.01

Peterson has maintained his fourth wife ran off with another man and is still alive.

NPR: Peterson Screams, Then Gets 38 Years For Murder

Lowe was engaged at the time but became pregnant during an affair with another man, jurors were told.

NPR: Jury Convicts Tenn Mother In Newborn Twins' Deaths

In his statement he described his "life partnership" with another man as a "gift and vocation from God".

BBC: Fresh support for gay bishop