Countervail is a verb that means to offset the effect of something.

The Latin phrase contra Valere (CONE tra vah LARE ay) means ‘be of worth against.’ When we countervail something, we create an equal weight. Here’s an example:

My attempt to countervail all the awful music my students listened to by playing opera in the classroom was not met with open arms. They simply didn’t want their awful music to be offset by my awful music.