1 A reversion to an earlier, more immature mode of thinking, feeling, or behaving.
2 In psychoanalysis, a defence mechanism whereby a person reverts to a form of behaviour, thinking, or object-relationship characteristic of an earlier stage of development in order to avoid or reduce anxiety. Libidinal regression is a retreat to an earlier libidinal stage, and tends to occur in response to conflict if there has been an earlier fixation (2); ego regression is a return to earlier modes of mental functioning, as when an adult behaves in a childlike manner under stress. The concept was introduced by Sigmund Freud (1856–1939) in 1900 in his book The Interpretation of Dreams (Standard Edition, IV-V, at pp. 533–48). See also regression in the service of the ego.
3 In statistics, a technique for analysing the association between one or more independent variables and a dependent variable. See multiple regression, regression analysis, regression towards the mean.
4 A backward glance while reading a line of text. [From Latin regressus a stepping back + -ion indicating an action, process, or state]