sleeper

noun

sleep·​er ˈslē-pər 

1

: one that sleeps

2

: a piece of timber, stone, or steel on or near the ground to support a superstructure, keep railroad rails in place, or receive floor joists : stringpiece

3

: sleeping car

4

: someone or something unpromising or unnoticed that suddenly attains prominence or value

the low-budget film became the summer's sleeper

5

: children's pajamas usually with feet

—usually used in plural

6

chiefly British : a small earring or stud worn to keep the hole of a pierced ear from closing

7

: mole entry 2 sense 4

Synonyms of sleeper

• slumberer

Examples of sleeper in a Sentence

Sleepers were awakened by the sound of a loud crash.

He may turn out to be the sleeper in this year's election.

The movie was the summer's sleeper.

The movie became the sleeper hit of the summer.

Recent Examples on the Web

Mattresses, Box Springs, and Mattress Toppers Much like most secondhand stores don't accept adult-sized mattresses, many don't accept kids' sleep items like crib mattresses, junior bed mattresses, mattress toppers, box springs, sleep and positioning aids, and co-sleepers. —Maria Sabella, The Spruce, 13 June 2026

For those trips when parents are able to get away for a few days by themselves, the Rangeline PL transforms seamlessly and quickly into a roomy two-sleeper. —New Atlas, 12 June 2026

Bedoya offers insights on this year’s biggest contenders, plus gives his favorites, sleepers and a look at Team USA’s strengths and weaknesses heading into the Cup. —Andre Fernandez, Miami Herald, 11 June 2026

The Beautyrest Black Mattress is a luxury innerspring designed for sleepers who want support without feeling stuck to a stiff surface. —Audrey Lee, Architectural Digest, 11 June 2026

Word History

First Known Use

12th century, in the meaning defined at sense 1

Phrases Containing sleeper

• heavy sleeper
• light sleeper
• sleeper cell
• sleeper sofa
• sound sleeper

Rhymes for sleeper

• beeper
• cheaper
• creeper
• deeper
• keeper
• reaper
• steeper
• sweeper
• beekeeper
• bookkeeper
• doorkeeper
• gamekeeper

Kids Definition

sleeper

noun

sleep·​er ˈslē-pər 

1

: one that sleeps

2

: a horizontal beam to support something on or near ground level

3

: sleeping car

4

: someone or something considered unlikely to succeed that suddenly becomes successful