1. an effect in which an activity or occurrence previously suppressed or prevented increases once the restrictions imposed on it are removed. The term is used particularly to denote the temporary reappearance of symptoms following abrupt discontinuation of a medication used for treatment. An example is rebound insomnia, in which the discontinuation of hypnotic agents, particularly short-acting benzodiazepines, results in a transitory return of insomnia, possibly of increased severity. Also called rebound effect.

2. a test that demonstrates loss of the ability of the cerebellum to control coordinated movement: If the individual extends the forearm against resistance and the resistance is suddenly removed, the hand or fist will snap back toward the chest. Also called Holmes’s phenomenon.