1. a recurring sleep state during which dreaming occurs; a state of rapidly shifting eye movements during sleep • Syn: paradoxical sleep, rapid eye movement sleep, REM sleep, rapid eye movement • Hypernyms: sleep, slumber 2.(Roentgen Equivalent Man) the dosage of ionizing radiation that will cause the same amount of injury to human tissue as 1 roentgen of X-rays • Hypernyms: radioactivity unit
