an active hostility or opposition, as between unfriendly orconflicting groups: the antagonism between the liberal and theconservative parties. .
2. an opposing force , pri…nciple, or tendency: Her plan to becomean actress met with the antagonism of her family. .
3. Physiology . an opposing action, as by one muscle in relationto another..
4. Biochemistry, Pharmacology . the opposing action ofsubstances, as drugs, that when taken together decreasethe effectiveness of at least one of them ( contrasted with synergism )..
5. Ecology . a. a relationship between two species of organisms in which the individuals of each species adversely affectthe other, as in competition..
b. the inhibition of the growth of one type of organism by adifferent type that is competing for the same ecological. (MORE)