<p><strong>Noun</strong></p><ul><li>the reversing of what has been done; annulling.</li><li>Synonyms: negation, reversal</li><li>a bringing to destruction, ruin, or disaster.</li><li>a cause of destruction or ruin.</li><li>the act of unfastening or loosing.</li><li>Psychiatry: an unconscious defense mechanism through which an attempt is made to reverse a psychologically unacceptable act by doing its opposite, usually repetitiously, in order to relieve anxiety.</li></ul>