regression

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The process or an instance of regressing, as to a less perfect or less developed state.
• noun Psychology Reversion to an earlier or less mature pattern of feeling or behavior.
• noun Medicine Subsidence of the symptoms or process of a disease.
• noun 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.
• noun Astronomy Retrograde motion of a celestial body.
• noun Geology A relative fall in sea level resulting in deposition of terrestrial strata over marine strata.

from The Century Dictionary.

• noun In mathematics, a discrete series which has a last element but no first.
• noun In statistics, the tendency of one variable phenomenon that is correlated with another to revert to the general type and not to equal the amount of deviation of the particular phenomenon with which it is correlated.
• noun In breeding, the decline toward mediocrity of offspring from the mean of the two parents. Sometimes called filial regression.
• noun The act of passing back or returning; retrogression.
• noun In astronomy, motion from east toward west.
• noun In geometry, contrary flexure; also, the course of a curve at a cusp.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of passing back or returning; retrogression; retrogradation.
• noun (Geom.) the line along which a surface turns back upon itself; -- called also a cuspidal edge.
• noun (Geom.) a cusp.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An action of regressing, a return to a previous state.
• noun psychotherapy A psychotherapeutic method whereby healing is facilitated by inducing the patient to act out behaviour typical of an earlier developmental stage.
• noun statistics An analytic method to measure the association of one or more independent variables with a dependent variable.
• noun statistics An equation using specified and associated data for two or more variables such that one variable can be estimated from the remaining variable(s).
• noun programming The reappearance of a bug in a piece of software that had previously been fixed.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an abnormal state in which development has stopped prematurely
• noun (psychiatry) a defense mechanism in which you flee from reality by assuming a more infantile state
• noun the relation between selected values of x and observed values of y (from which the most probable value of y can be predicted for any value of x)
• noun returning to a former state