Medical Definition of REM sleep
: a state of sleep that recurs cyclically several times during a normal period of sleep and that is characterized by increased neuronal activity of the forebrain and midbrain, by depressed muscle tone, and especially in humans by dreaming, rapid eye movements, and vascular congestion of the sex organs—called also desynchronized sleep, paradoxical sleep, rapid eye movement sleep; compare slow-wave sleep
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Dictionary: Definition of "REM sleep"
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