Rapid eye movement sleep
(RA-pid I MOOV-ment sleep) One of the five stages of sleep. During rapid eye movement sleep, the eyes move rapidly while closed and dreams occur. Rapid eye movement sleep is the lightest stage of sleep, during which a person may wake easily. During several hours of normal sleep, a person will go through several sleep cycles that include rapid eye movement sleep and the 4 stages of non-rapid eye movement (light to deep sleep). Also called REM sleep.