枉费

They tried in vain to persuade her to go.

他们极劝，枉费了一番口舌。

The reactionary government tried vainly to take the steam out of the protest movement.

反政府枉费心机地企图削弱这场抗议运。

Those who protested against the president's decision were actually barking at the moon, since they were in a powerless minority.

由于他们属于软弱无的少数, 他们反对总统的决定实际上枉费唇舌。