It was just a one-off; it won't happen again.

这事绝无仅有；不会再发生了。

《牛津词典》

The technology, Strano said, could one day be used to light the rooms or even to turn trees into self-powered street lamps. In the future, the team hopes to develop a version of the technology that can be sprayed onto plant leaves in a one-off treatment that would last the plant's lifetime.

斯特拉诺表示，该技术将来可能用于房间照明，甚至可以将树木改造为自供电路灯。该团队希望未来可以开发此技术的新形式，用于喷洒植物叶片，一次操作，终生有效。

youdao

A one-off jump in commodity prices is not inflation. Nor need such a jump cause inflation.

大宗商品价格的一次性跃升不是通胀，也不一定会引发通胀。

youdao

You would not want to get off one horse and on to another in the middle of a river.

VOA: special.2009.07.12

When demons are cast out by the apostles and sent into a herd of pigs, and the pigs go running off a cliff and die; that's one image.

第一个是魔鬼们被使徒们赶出了天界,赶到了一群猪的中间，然后那些猪就跑向了悬崖,摔死在了那里。

耶鲁公开课 - 1945年后的美国小说课程节选

So you say well, rather than rushing off and fixing this one bug, let me pull back and ask, bug is this a systematic mistake that I've made throughout the program?

因此我们应该回头想想,这是不是我在整个程序中都，在犯的一个系统性错误，而不是匆匆忙忙的去修复这一个,如果确实是系统性错误的话？

麻省理工公开课 - 计算机科学及编程导论课程节选

It would be fun to make a secret surf level or something, like a one off.

FORBES: Connect

And this isn't a one off - many other manufacturers are coming home.

BBC: Is 'Made in the USA' coming back?

Rather than this being a one off, we also lost young Ezequiel Fryers for the very same reason.

FORBES: Manchester United: where would we be without the Glazers?