1. A dark horse

黑马，实力难以预测的竞争者或出人意料的获胜者

We never expected that he would be the champion in the race. He was such a dark horse!

我们从未预料到他会成为比赛中的冠军。他真是一匹黑马！

2. Closing the stable door after the horse has bolted

失马锁厩，形容为时已晚

Introducing tighter security measures after the break in seems to me like closing the stable door after the horse has bolted.

在被破门而入之后再引进更牢固的安全措施，在我看来为时已晚。

3. A horse of another color/a horse of a different color

另当别论，完全另外一回事

Taking the exam is one thing but passing it is a horse of a different color.

参加考试是一回事，通过考试又是另一回事。

4. Beat/flog a dead horse

在已经发生的事上浪费时间，做无用功

Do you think It's worth me writing to a few more recruitment agencies, or am I just beating a dead horse?

你觉得我再给一些招聘公司写信值不值？还是我只是在浪费时间？

5. Get off your high horse

放下架子，别那么趾高气扬

If you would get off your high horse for one minute and listen to your colleagues, you would find that they have some great ideas for this project.

如果你能有一会放下架子，听听同事的意见，你会发现他们对于这个项目有这非常出色的想法。

6. Don't put the cart before the horse

不要本末倒置，做事顺序不要颠倒

There's no point trying to write the report when you haven't got a clear idea of what to write. You don't want to put the cart before the horse.

在你还没有清晰的想法之前就去写报告是没有意义的。你不应该本末倒置。