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[slee-ping] /ˈsli pɪŋ/
the condition of being asleep.
of, relating to, or having accommodations for sleeping:
a sleeping compartment.
used to sleep in or on:
a sleeping jacket.
used to induce or aid sleep or while asleep:
sleeping mask.
Origin of sleeping
1250-1300; Middle English; see sleep, -ing1, -ing2
Related forms
unsleeping, adjective


[sleep] /slip/
verb (used without object), slept, sleeping.
to take the rest afforded by a suspension of voluntary bodily functions and the natural suspension, complete or partial, of consciousness; cease being awake.
Botany. to assume, especially at night, a state similar to the sleep of animals, marked by closing of petals, leaves, etc.
to be dormant, quiescent, or inactive, as faculties.
to be careless or unalert; allow one's alertness, vigilance, or attentiveness to lie dormant:
While England slept, Germany prepared for war.
to lie in death:
They are sleeping in their tombs.
verb (used with object), slept, sleeping.
to take rest in (a specified kind of sleep):
He slept the sleep of the innocent.
to accommodate for sleeping; have sleeping accommodations for:
This trailer sleeps three people.
to spend or pass in sleep (usually followed by away or out):
to sleep the day away.
to recover from the effects of (a headache, hangover, etc.) by sleeping (usually followed by off or away).
the state of a person, animal, or plant that sleeps.
a period of sleeping:
a brief sleep.
dormancy or inactivity.
the repose of death.
sleeper (def 10).
Verb phrases
sleep around, Informal. to have sexual relations with many partners, especially in a casual way; be sexually promiscuous.
sleep in,
  1. (especially of domestic help) to sleep where one is employed.
  2. to sleep beyond one's usual time of arising.
sleep on, to postpone making a decision about for at least a day:
to sleep on a proposal till the end of the week.
sleep out,
  1. (especially of domestic help) to sleep away from one's place of employment.
  2. Chiefly Northern U.S. to sleep away from one's home.
  3. to sleep outdoors.
sleep over, to spend one or more nights in a place other than one's own home:
Two friends will sleep over this weekend.
sleep together, to be sexual partners; have a sexual relationship.
sleep with, to have sexual relations with.
put to sleep, to put (an animal) to death in a humane way:
to put a sick old dog to sleep.
before 900; (noun) Middle English; Old English slēp (Anglian), slǣp, slāp; cognate with Dutch slaap, German Schlaf, Gothic slēps; (v.) Middle English slepen, Old English slēpan, slǣpan, slāpan, cognate with Old Saxon slāpan, Gothic slēpan
Related forms
sleepful, adjective
sleeplike, adjective
antisleep, adjective
undersleep, verb (used without object), underslept, undersleeping.
1. slumber, nap, drowse, doze. 10. rest, repose. 11. nap. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for sleeping
Contemporary Examples
Historical Examples
  • No, I'm not sleeping at night nor working reg'lar in the day neither.

    The Manxman Hall Caine
  • It was like walking by a graveyard where some one was sleeping that he loved.

    The Man from the Bitter Roots Caroline Lockhart
  • "I hear it every day, sleeping and waking," said his mother, putting her hands to her ears.

  • He came with the pole and the ropes in his hand to where Thor was sleeping.

    The Children of Odin Padraic Colum
  • As in Japanese houses, mats are used for sitting and sleeping purposes.

    The Empire of the East H. B. Montgomery
British Dictionary definitions for sleeping


a periodic state of physiological rest during which consciousness is suspended and metabolic rate is decreased See also paradoxical sleep
(botany) the nontechnical name for nyctitropism
a period spent sleeping
a state of quiescence or dormancy
a poetic or euphemistic word for death
(informal) the dried mucoid particles often found in the corners of the eyes after sleeping
verb sleeps, sleeping, slept
(intransitive) to be in or as in the state of sleep
(intransitive) (of plants) to show nyctitropism
(intransitive) to be inactive or quiescent
(transitive) to have sleeping accommodation for (a certain number): the boat could sleep six
(transitive) foll by away. to pass (time) sleeping
(intransitive) to fail to pay attention
(intransitive) (poetic or euphemistic) to be dead
sleep on it, to give (something) extended consideration, esp overnight
Word Origin
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
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Word Origin and History for sleeping

c.1300, past participle adjective from sleep (v.). Sleeping-pill is from 1660s; sleeping-bag is from 1850; sleeping sickness as a specific African tropical disease is first recorded 1875; sleeping has been used since late 14c. for diseases marked by morbid conditions. Sleeping Beauty (1729) is Perrault's La belle au bois dormant.



Old English slæpan "to be or fall asleep; be dormant or inactive" (class VII strong verb; past tense slep, past participle slæpen), from Proto-Germanic *slepan (cf. Old Saxon slapan, Old Frisian slepa, Middle Dutch slapen, Dutch slapen, Old High German slafen, German schlafen, Gothic slepan "to sleep"), from PIE root *sleb- "to be weak, sleep" (cf. Old Church Slavonic slabu "lax, weak," Lithuanian silpnas "weak"), which perhaps is connected to the root of slack (adj.). Sleep with "do the sex act with" is in Old English:

Gif hwa fæmnan beswice unbeweddode, and hire mid slæpe ... [Laws of King Alfred, c.900]
Related: Slept; sleeping. Sleep around first attested 1928.


Old English slæp "sleep, sleepiness, inactivity," from Proto-Germanic *slepaz, from the root of sleep (v.); cf. cognate Old Saxon slap, Old Frisian slep, Middle Dutch slæp, Dutch slaap, Old High German slaf, German Schlaf, Gothic sleps.

Personified in English from late 14c., on model of Latin Somnus), Greek Hypnos. Figurative use for "repose of death" was in Old English; to put (an animal) to sleep "kill painlessly" is recorded from 1923 (a similar imagery is in cemetery). Sleep deprivation attested from 1906. Sleep-walker "somnambulist" is attested from 1747; sleep-walking is from 1840. To be able to do something in (one's) sleep "easily" is recorded from 1953.

Online Etymology Dictionary, © 2010 Douglas Harper
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sleeping in Medicine

sleep (slēp)
A natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli. During sleep the brain in humans and other mammals undergoes a characteristic cycle of brain-wave activity that includes intervals of dreaming. v. slept (slěpt), sleep·ing, sleeps
To be in the state of sleep.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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sleeping in Science
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 © 2002. Published by Houghton Mifflin. All rights reserved.
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Idioms and Phrases with sleeping
The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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