noun (n)

• the relation between propositions that cannot both be true at the same time(noun.linkdef)

  Synonym:
  inconsistency, mutual exclusiveness, repugnance
  

  source: wordnet30
• (immunology) the degree to which the body's immune system will try to reject foreign material (as transfused blood or transplanted tissue)(noun.state)

  source: wordnet30
• the quality of being unable to exist or work in congenial combination(noun.attribute)

  Antonym:
  compatibility
  

  source: wordnet30
• The quality or state of being incompatible; inconsistency; irreconcilableness.(noun)

  source: webster1913