[ sleep ]
See synonyms for: sleepsleepingslept on

verb (used without object),slept, sleep·ing.
  1. to take the rest afforded by a suspension of voluntary bodily functions and the natural suspension, complete or partial, of consciousness; cease being awake.

  2. Botany. to assume, especially at night, a state similar to the sleep of animals, marked by closing of petals, leaves, etc.

  1. to be dormant, quiescent, or inactive, as faculties.

  2. to be careless or unalert; allow one's alertness, vigilance, or attentiveness to lie dormant: While England slept, Germany prepared for war.

  3. to lie in death: They are sleeping in their tombs.

verb (used with object),slept, sleep·ing.
  1. to take rest in (a specified kind of sleep): He slept the sleep of the innocent.

  2. to accommodate for sleeping; have sleeping accommodations for: This trailer sleeps three people.

  1. to spend or pass in sleep (usually followed by away or out): to sleep the day away.

  2. to recover from the effects of (a headache, hangover, etc.) by sleeping (usually followed by off or away).

  1. the state of a person, animal, or plant that sleeps.

  2. a period of sleeping: a brief sleep.

  1. dormancy or inactivity.

  2. the repose of death.

Verb Phrases
  1. sleep around, Informal. to have sexual relations with many partners, especially in a casual way; be sexually promiscuous.

  2. sleep in,

    • (especially of domestic help) to sleep where one is employed.

    • to sleep beyond one's usual time of arising.

  1. sleep on, to postpone making a decision about for at least a day: to sleep on a proposal till the end of the week.

  2. sleep out,

    • (especially of domestic help) to sleep away from one's place of employment.

    • Chiefly Northern U.S. to sleep away from one's home.

    • to sleep outdoors.

  3. sleep over, to spend one or more nights in a place other than one's own home: Two friends will sleep over this weekend.

  4. sleep together, to be sexual partners; have a sexual relationship.

  5. sleep with, to have sexual relations with.

Idioms about sleep

  1. put to sleep, to put (an animal) to death in a humane way: to put a sick old dog to sleep.

Origin of sleep

First recorded before 900; (for the noun) Middle English; Old English slēp (Anglian), slǣp, slāp; cognate with Dutch slaap, German Schlaf, Gothic slēps; (for the verb) Middle English slepen, Old English slēpan, slǣpan, slāpan, cognate with Old Saxon slāpan, Gothic slēpan

Other words for sleep

Other words from sleep

  • sleepful, adjective
  • sleeplike, adjective
  • an·ti·sleep, adjective
  • un·der·sleep, verb (used without object), un·der·slept, un·der·sleep·ing.

Words Nearby sleep Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use sleep in a sentence

British Dictionary definitions for sleep


/ (sliːp) /

  1. a periodic state of physiological rest during which consciousness is suspended and metabolic rate is decreased: See also paradoxical sleep

  2. botany the nontechnical name for nyctitropism

  1. a period spent sleeping

  2. a state of quiescence or dormancy

  3. a poetic or euphemistic word for death

  4. informal the dried mucoid particles often found in the corners of the eyes after sleeping

verbsleeps, sleeping or slept
  1. (intr) to be in or as in the state of sleep

  2. (intr) (of plants) to show nyctitropism

  1. (intr) to be inactive or quiescent

  2. (tr) to have sleeping accommodation for (a certain number): the boat could sleep six

  3. (tr foll by away) to pass (time) sleeping

  4. (intr) to fail to pay attention

  5. (intr) poetic, or euphemistic to be dead

  6. sleep on it to give (something) extended consideration, esp overnight

Origin of sleep

Old English slǣpan; related to Old Frisian slēpa, Old Saxon slāpan, Old High German slāfan, German schlaff limp

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for sleep


[ slēp ]

  1. A natural, reversible state of rest in most vertebrate animals, occurring at regular intervals and necessary for the maintenance of health. During sleep, the eyes usually close, the muscles relax, and responsiveness to external stimuli decreases. Growth and repair of the tissues of the body are thought to occur, and energy is conserved and stored. In humans and certain other animals, sleep occurs in five stages, the first four consisting of non-REM sleep and the last stage consisting of REM sleep. These stages constitute a sleep cycle that repeats itself about five times during a normal episode of sleep. Each cycle is longer that the one preceding it because the length of the REM stage increases with every cycle until waking occurs. Stage I is characterized by drowsiness, Stage II by light sleep, and Stages III and IV by deep sleep. Stages II and III repeat themselves before REM sleep (Stage V), which occurs about 90 minutes after the onset of sleep. During REM sleep, dreams occur, and memory is thought to be organized. In the stages of non-REM sleep, there are no dreams, and brain activity decreases while the body recovers from wakeful activity. The amount and periodicity of sleep in humans vary with age, with infants sleeping frequently for shorter periods, and mature adults sleeping for longer uninterrupted periods. See also non-REM sleep REM sleep.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Other Idioms and Phrases with sleep


In addition to the idioms beginning with sleep

  • sleep around
  • sleep a wink, not
  • sleep in
  • sleep like a log
  • sleep on something
  • sleep out
  • sleep over
  • sleep through
  • sleep with

also see:

  • let sleeping dogs lie
  • lose sleep over
  • put to sleep

Also see underasleep.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.