rem

(noun) a recurring sleep state during which dreaming occurs; a state of rapidly shifting eye movements during sleep. Synonyms: paradoxical sleep, rapid eye movement sleep, REM sleep, rapid eye movement, REM.

(noun) (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. Synonyms: REM.