REM sleepREM sleep
A period of sleep during which dreaming takes place, characterized by rapid periodic twitching movements of the eye muscles and other physiological changes, such as accelerated respiration and heart rate, increased brain activity, and muscle relaxation. REM sleep is the fifth and last stage of sleep that occurs in the sleep cycle, preceded by four stages of non-REM sleep. Also called paradoxical sleep.
Origin of REM sleepr(apid) e(ye) m(ovement).