Definition
To waste effort on a futile endeavor that has no chance of succeeding.
徒勞無功，做毫無意義的事情。
Trying to convince him to change his mind is like beating a dead horse; he's already made up his mind.
試圖說服他改變主意就像在鞭打一匹死馬；他已經下定決心了。
They keep trying to get the project back on track, but I think they're just beating a dead horse.
他們一直試圖讓項目重回正軌，但我認為他們只是在做無用功。
There's no point in continuing to argue about this issue; we're just beating a dead horse.
繼續爭論這個問題毫無意義；我們只是在做無用功。