Today, we talk about beating a dead horse.

今天，我们谈论的是“beating a dead horse”。

But beating a dead horse would be pointless – because it's dead.

但抽打一匹死马是没有意义的——因为它已经死了。

Sometimes a person fights a battle that has been decided or keeps arguing a question that has been settled. We say this is like " beating a dead horse."

有时，一个人可能一直就已经决定了的战争而战斗，或者一直争论已经解决了的问题。我们说，这简直是白费口舌(就好象beating a dead horse)。

If you don't want to say to them, " Now you're just beating a dead horse, " you can say, " Look, we've gone over the same ground and nothing has changed. So, can we please change the topic? "

如果你不想对他们说，“现在你只是在做无用功”，你可以说，“看，我们已经讨论过同样的问题，没有任何改变。所以，我们能不能换个话题？”