A countervailing force, power, or opinion is one which is of equal strength to another one but is its opposite or opposes it.
例句
Their strategy is expansionist and imperialist, and it is greatest in effect, of course, when there is no countervailing power...他們的策略是擴張性的、帶有帝國主義特色，當沒有抗衡力量的時候自然也就被發揮到了極致。There were two central and countervailing forces in the life of Nikola Tesla.在尼古拉·特斯拉的生活中存在著兩股非常重要而且相互抗衡的力量。