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