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

• 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

Allergy-prone sleepers can still indulge in hotel-level comfort with Boll & Branch’s down alternative pillow. —Julia Harrison, Architectural Digest, 8 Oct. 2025

There are a select few who carry the sleepers on their backs. —Stan Son, New York Times, 7 Oct. 2025

Bedsure Cooling Comforter Hot sleepers, rejoice—this cooling quilt is made for you. —Sheri Kaz, Better Homes & Gardens, 7 Oct. 2025

The material is luxuriously soft and cool to the touch (perfect for hot sleepers like me), with a light and breathable feel that works year-round. —Jeaneen Russell, PEOPLE, 7 Oct. 2025

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