Emily Dickinson Lexicon

COUN-TER-VAIL', v.t. [counter and L. valeo, to avail or be strong.]

To act against with equal force, or power; to equal; to act with equivalent effect against any thing; to balance; to compensate; as, the profit will hardly countervail the inconveniences. Although the enemy could not countervail the king's damage. Esth. vii.