Definition for Antagonism
From Biology Forums Dictionary
1) In physiology, it is the result of the interaction between structures, chemical agents, or diseases that have opposing physiological functions or effects
2) In biochemistry, it is the reduced overall effect due to the opposing effects of different chemical groups or agents
2) In cell biology, it is the binding of a molecule to the target site of the agonist, thus preventing the agonist from exerting its effect (i.e. stimulatory effect) on the target site.