- (transitive) to oppose, neutralize, or mitigate the effects of by contrary action; check
WordReference Random House Learner's Dictionary of American English © 2026
coun•ter•act /ˌkaʊntərˈækt/USA pronunciation
v. [~ + object]
coun•ter•ac•tion /ˌkaʊntərˈækʃən/USA pronunciation n. [countable]
coun•ter•ac•tive, adj.
coun•ter•ac•tive•ly, adv.
WordReference Random House Unabridged Dictionary of American English © 2026- to act in opposition to; frustrate by contrary action:This medicine will counteract the effects of the disease.
coun•ter•ac•tion /ˌkaʊntərˈækʃən/USA pronunciation n. [countable]
coun•ter•ac•tive, adj.
coun•ter•ac•tive•ly, adv.
coun•ter•act
(koun′tər akt′),USA pronunciation v.t.
coun′ter•ac′tant, adj.
coun′ter•act′er, coun′ter•ac′tor, n.
coun′ter•act′ing•ly, adv.
coun′ter•ac′tion, n.
coun′ter•ac′tive, adj.
coun′ter•ac′tive•ly, adv.
- to act in opposition to;
frustrate by contrary action.
- counter- + act 1670–80
coun′ter•act′er, coun′ter•ac′tor, n.
coun′ter•act′ing•ly, adv.
coun′ter•ac′tion, n.
coun′ter•ac′tive, adj.
coun′ter•ac′tive•ly, adv.
- neutralize, counterbalance, contravene, thwart.
Collins Concise English Dictionary © HarperCollins Publishers::
counteract /ˌkaʊntərˈækt/ vb
'counteract' also found in these entries (note: many are not synonyms or translations):
antagonize
- anti-inflationary
- Bach flower remedy
- correct
- counterespionage
- countervailing duty
- detoxicate
- disarming
- guard ring
- martingale
- prestressed concrete
- squeeze
- stabilizer
- tail rotor
- additive
- antibugging
- antidote
- antirecessionary
- ballast
- counterpoise
- countervail
- cushion
- damage control
- dragging piece
- Le Châtelier principle
- moisturize
- moly
- negative
- neutralize
- offset
- open universe
- reality check
- remedy
- resist
- uncounteracted
- white magic
- summerize