noun.
An assertion of the direct opposite to what has been said or affirmed; denial; contrary declaration.
noun.
Opposition, whether by argument or conduct.
noun.
Direct, opposition or repugnancy; absolute inconsistency; specifically, the relation of two propositions which are so opposed that one must be false and one must be true.
noun.
Figuratively, a person who or a thing which is self-contradictory or inconsistent.