Main Entry: coun·ter·act

Pronunciation: \ˌkau̇n-tər-ˈakt\

Function: transitive verb

Date: 1655

: to make ineffective or restrain or neutralize the usually ill effects of by means of an opposite force, action, or influence <a drug used to counteract fatigue>

— coun·ter·ac·tion \-ˈak-shən\ noun

— coun·ter·ac·tive \-ˈak-tiv\ adjective