Definition of counteract
- a drug used to counteract fatigue
The drug will counteract the poison.
this medication will counteract the symptoms but it won't kill the infection
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'counteract.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
: act against (something) : to cause (something) to have less of an effect or to have no effect at all
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