lost cause

Noun

idiomatic

(idiomatic) A person or thing that is hopeless or futile.

Japanese Meaning

救いようのない人や物、手の施しようがなく無駄とされる存在

Trying to convince him to change his risky habits was a lost cause, but I couldn't stop trying.

彼に危険な習慣を改めさせようと説得するのは見込みのないことだったが、私はあきらめることができなかった。

Sense（1）

(idiomatic) A person or thing that is hopeless or futile.

He has already made up his mind, and it's a lost cause to try to change it.

lost causes

（ plural ）