Definition of Countervail

To counterbalance; to avail against with equal force or virtue; to compensate for or serve as an equivalent of or substitute for
—Countervail livery. At common law, a release was a form of transfer of real estate where some right to it existed in one person but the actual possession was in another; and the possession in such case was said to "countervail livery," that is, it; supplied the place of and rendered unnecessary the open and notorious delivery of possession required in other cases. Miller v. Emans, 19 N. Y. 387.
—Countervailing equity. See Equity.