<p><strong>Noun</strong></p><ul><li>an active hostility or opposition, as between unfriendly or conflicting groups: the antagonism between the liberal and the conservative parties</li><li>Synonyms: strife, friction, conflict</li><li>an opposing force, principle, or tendency: Her plan to become an actress met with the antagonism of her family</li><li>Synonyms: animosity</li><li>Physiology: an opposing action, as by one muscle in relation to another</li><li>Biochemistry, Pharmacology: the opposing action of substances, as drugs, that when taken together decrease the effectiveness of at least one of them (synergism)</li><li>Ecology: a relationship between two species of organisms in which the individuals of each species adversely affect the other, as in competition</li><li>the inhibition of the growth of one type of organism by a different type that is competing for the same ecological niche</li></ul>