n. 1. The process or an instance of regressing, as to a less perfect or less developed state.
2. Psychology In psychoanalytic theory, reversion to an earlier or less mature stage of psychological development.
3. Medicine Subsidence of the symptoms or process of a disease.
4. Statistics A technique for predicting the value of a dependent variable as a function of one or more independent variables in the presence of random error.
5. Astronomy Retrograde motion of a celestial body.
6. Geology A relative fall in sea level resulting in deposition of terrestrial strata over marine strata.