- To counteract is to act in opposition to or against some force in order to neutralize the force.
When you try to grab a rope and your friend pulls it away from you in the other direction, this is an example of a time when your friend counteracts your efforts.
counteract definition by Webster's New World
counteract definition by American Heritage Dictionary
transitive verb coun·ter·act·ed, coun·ter·act·ing, coun·ter·acts
- counˌter·acˈtion noun
- counˌter·acˈtive adjective
- counˌter·acˈtive·ly adverb