from The American Heritage® Dictionary of the English Language, 4th Edition
- transitive v. To oppose and mitigate the effects of by contrary action; check.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. To act in opposition to; to hinder, defeat, or frustrate, by contrary agency or influence; as, to counteract the effect of medicines; to counteract good advice.
from the GNU version of the Collaborative International Dictionary of English
- transitive v. To act in opposition to; to hinder, defeat, or frustrate, by contrary agency or influence.
from The Century Dictionary and Cyclopedia
- To act in opposition to; hinder, defeat, or frustrate by contrary agency.
- Synonyms To thwart, check, contravene, cross, neutralize.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- v. act in opposition to
- v. oppose and mitigate the effects of by contrary actions
- v. oppose or check by a counteraction
- v. destroy property or hinder normal operations
From counter- + act. (Wiktionary)