sleeper

American  

[slee-per] / ˈsli pər /

noun

• sleepers
  plural

1. a person or thing that sleeps.

2. a heavy horizontal timber for distributing loads.

3. Building Trades.

   1. any long wooden, metal, or stone piece lying horizontally as a sill or footing.

   2. any of a number of wooden pieces, laid upon the ground or upon masonry or concrete, to which floorboards are nailed.

4. a sleeping car.

5. Informal. something or someone that becomes unexpectedly successful or important after a period of being unnoticed, ignored, or considered unpromising or a failure.

   The play was the sleeper of the season.

6. merchandise that is not quickly sold because its value is not immediately recognized.

7. Often sleepers. one-piece or two-piece pajamas with feet, especially for children.

8. bunting.

9. a sofa, chair, or other piece of furniture that is designed to open up or unfold into a bed; convertible.

10. Also called sleep, sand.  a globule that forms at the inner corner of the eye, especially during sleep, from the accumulated secretion of the glands of the eyelid.

11. any of several gobioid fishes of the family Eleotridae, of tropical seas, most species of which have the habit of resting quietly on the bottom.

12. Slang. a spy; mole.

13. Slang. a juvenile delinquent sentenced to serve more than nine months.

14. Bowling. a pin that is hidden from view by another pin.

15. Chiefly British. a timber or beam laid in a railroad track, serving as a foundation or support for the rails; tie.

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sleeper British  

/ ˈsliːpə /

noun

1. a person, animal, or thing that sleeps

2. a railway sleeping car or compartment

3. US and Canadian equivalent: tie.  one of the blocks supporting the rails on a railway track

4. a heavy timber beam, esp one that is laid horizontally on the ground

5. a small plain gold circle worn in a pierced ear lobe to prevent the hole from closing up

6. a wrestling hold in which a wrestler presses the sides of his opponent's neck, causing him to pass out

7. an unbranded calf

8. Also called: sleeper goby.  any gobioid fish of the family Eleotridae, of brackish or fresh tropical waters, resembling the gobies but lacking a ventral sucker

9. informal a person or thing that achieves unexpected success after an initial period of obscurity

10. a spy planted in advance for future use, but not currently active

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Other Word Forms

Noun Inflected Forms

• sleepers
  plural

Etymology

Origin of sleeper

Middle English word dating back to 1175–1225; see origin at sleep, -er ¹

Explanation

A sleeper is something that succeeds when no one thought it would. That low-tech movie about shark attacks that you shot on vacation and edited in your basement? It could be a sleeper if you market it in the right way. You probably know that sleeper can be used in an obvious sense to refer to someone who is asleep. But you also may hear the word used to describe something that becomes an unexpected success, like "a sleeper of a film" featuring unknown actors that ends up becoming the big summer hit. This sense of the word may have originated in the world of gambling in the nineteenth century. When a card player unexpectedly drew a winning card, the card was called "a sleeper."

Example Sentences

See Examples For:

sleeper sleepers

If you’re in the mood for a thriller: Hulu’s sleeper hit Furious—which just wrapped up its first season—stars a trio of knockout performances, but one of its stars towers above the rest.

From Slate ● Aug. 31, 2026

Reports compiled by BBC Monitoring say the army continues to carry out security sweeps across greater Khartoum, targeting alleged RSF sleeper cells, undocumented foreigners and criminals involved in illegal activities.

From BBC ● Aug. 28, 2026

"I'm also a light sleeper and was getting worried about the effects on myself," says Wen.

From Science Daily ● Aug. 24, 2026

“Widow’s Bay” is this season’s sleeper hit because the show is a horror trope clearinghouse.

From Salon ● Jun. 18, 2026

Blanca is not a light sleeper, so I got up thinking I didn’t have to be very quiet.

From "Bodega Dreams" by Ernesto Quinonez

"Our study suggests there may be different biological pathways between long and short sleepers that lead to the same outcome, late-life depression, and we shouldn't treat them the same way."

From Science Daily ● Aug. 24, 2026

The number of rough sleepers in England reached a record 4,793 in 2025, according to government figures.

From Barron's ● Aug. 19, 2026

The benefits were observed in both healthy sleepers and participants experiencing some sleep difficulties.

From Science Daily ● Aug. 7, 2026

Where the numbers were able to be compared to official government data, the census found 10 times as many female rough sleepers.

From BBC ● Jun. 10, 2026

Performers emerge from sleepers closer to the back of the train and of obviously better quality.

From "Water for Elephants" by Sara Gruen

Related Words

• agent
• detective
• informer
• investigator
• mole
• operative
• secret agent
• secret service
• undercover agent