/un dooh"ing/ , n.
1. the reversing of what has been done; annulling.
2. a bringing to destruction, ruin, or disaster.
3. a cause of destruction or ruin.
4. the act of unfastening or loosing.
5. 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.
[ 1300-50; ME; see UNDO, -ING 1 ]
Syn. 1. reversal, negation, thwarting.