Main Entry: an·tag·o·nism

Pronunciation: \an-ˈtag-ə-ˌniz-əm\

Function: noun

: opposition in physiological action: a : contrariety in the effect of contraction of muscles (as the extensors and flexors of a part) b : interaction of two or more substances such that the action of any one of them on living cells or tissues is lessened (as by interference with the uptake or by an opposing physiological reaction)—compare synergism