counteractant,n.|kaʊntərˈæktənt| [f.prec. + -ant1, after stimulant, etc.] A counteracting agency or force. 1884Pall Mall G. 5 Dec. 5/1 [This] is the best possible counteractant of the disloyal utterances.1891Harper's Mag. Apr. 752/1 It is a great rectifier of style and counter⁓actant to mannerism.