Open English Wordnet
Nouns
(n)contradictorytwo propositions are contradictories if both cannot be true (or both cannot be false) at the same time
Adjectives
(s)contradictoryof words or propositions so related that both cannot be true and both cannot be false“`perfect' and `imperfect' are contradictory terms”
(s)at odds, conflicting, contradictory, self-contradictoryin disagreement“the figures are at odds with our findings”, “contradictory attributes of unjust justice and loving vindictiveness” (John Morley)