Antagonism, n.
Etymology: [Gr. antagonisme. See Agony.]
Opposition of action; counteraction or contrariety of things or principles.
Note: We speak of antagonism between two things, to or against a thing, and sometimes with a thing.
Shades of meaning
Fernald has no entry of its own for antagonism; he lists it under antipathy, enmity.
Where he writes about it:
Antagonism may result from the necessity of circumstances; opposition may spring from conflicting views or interests; abhorrence and detestation may be the result of religious and moral training; distaste and disgust may be acquired; aversion is a deep and permanent dislike. — from antipathy
Antagonism, as between two competing authors or merchants, does not necessarily imply enmity, but ordinarily suggests a shade, at least, of hostile feeling. — from enmity