Coun`ter*vail" (koun`t?r-v?l"), v. t. [imp. & p. p. Countervailed (-v?ld); p. pr. & vb. n. Countervailing.] [OF. contrevaloir; contre (L. contra) + valoir to avail, fr. L. valere to be strong, avail. See Vallant.] To act against with equal force, power, or effect; to thwart or overcome by such action; to furnish an equivalent to or for; to counterbalance; to compensate.

Upon balancing the account, the profit at last will hardly countervail the inconveniences that go allong with it.
L'Estrange.

Coun"ter*vail` (koun"t?r-v?l`), n. Power or value sufficient to obviate any effect; equal weight, strength, or value; equivalent; compensation; requital. [Obs.]

Surely, the present pleasure of a sinful act is a poor countervail for the bitterness of the review.
South.