#1 counteract v. [antagonize, antagonise] act in opposition to. wn
#2 counteract v. [countercheck] oppose or check by a counteraction. wn
#3 counteract v. [countervail, neutralize, counterbalance] oppose and mitigate the effects of by contrary actions; "This will counteract the foolish actions of my colleagues". wn
#4 counteract v. [sabotage, undermine, countermine, subvert, weaken] destroy property or hinder normal operations; "The Resistance sabotaged railroad operations during the war". wn
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