1 In psychoanalysis, the enactment rather than recollection of past events, especially enactments relating to the transference during therapy. It is often impulsive and aggressive, and it is usually uncharacteristic of the patient's normal behaviour. The concept was introduced by Sigmund Freud (1856–1939) in An Outline of Psycho-Analysis (1938/40): the patient ‘acts it [the past event] before us, as it were, rather than reporting it to us’ (Standard Edition, XXIII, pp. 144–207, at p. 176). See also acting in.
2 A defence mechanism in which unconscious emotional conflicts or impulses are dealt with by actions, including parapraxes, rather than thought or contemplation. act out vb.