[coun.ter.vail] vb [ME countrevailen, fr. MF contrevaloir, fr. contre- counter- + valoir to be worth, fr. L valere--more at wield] vt (14c) 1: to compensate for
2. archaic: equal, match
3: to exert force against: counteract ~ vi: to exert force against an opposing and often bad or harmful force or influence