slow-wave sleep

noun Physiology.
  1. a recurrent period of deep sleep, typically totaling five or six hours a night, distinguished by the presence of slow brain waves and by very little dreaming.
Compare REM sleep.

Origin of slow-wave sleep

First recorded in 1965–70
Also called S sleep. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018