noun

• An action of regressing, a return to a previous state.
• An action of travelling mentally back in time.
• (psychotherapy) A psychotherapeutic method whereby healing is facilitated by inducing the patient to act out behaviour typical of an earlier developmental stage.
• (statistics) An analytic method to measure the association of one or more independent variables with a dependent variable.
• (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).
• (programming) The reappearance of a bug in a piece of software that had previously been fixed.
• (medicine) The diminishing of a cellular mass like a tumor, or of an organ size.
• (exercise) The making an exercise less straining to perform by manipulating the details of its performance like loaded weight, range of motion, angle, speed.