1. Hostility that results in active resistance, opposition, or contentiousness. See Synonyms at enmity.
2. The condition of being an opposing principle, force, or factor: the inherent antagonism of capitalism and socialism.
3. Biochemistry Interference in the physiological action of a chemical substance by another having a similar structure.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.