noun

• An assertion of untruth.
• (logic) The negation in logic.
• A refusal or failure to provide or grant something that is requested or desired.
• Refusal to believe that a problem exists.
• Refusal to admit responsibility for wrongdoing.
• Negationism, denialism of historical facts or accepted interpretation.
• (psychology) A defense mechanism involving a refusal to accept the truth of a phenomenon or prospect.
• A disownment or disavowal