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 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

What player can be the sleeper/X factor on the playoff teams? — Shakeia Taylor, New York Times, 15 Sep. 2026

But light-sensitive sleepers need not worry—an interior curtain can be drawn to keep out the sunshine and maintain privacy. — Morgan Goldberg, Architectural Digest, 11 Sep. 2026

The Cougars played for the title a season ago and are widely expected to do so again, but the Wildcats are a popular sleeper pick by some conference watchers. — Eddie Timanus, USA Today, 11 Sep. 2026

Droves of customers are also upgrading their bedding with these all-cotton bed sheets that are ideal for hot sleepers and this bubble throw blanket that’s cozy during extra-cool nights. — Clara McMahon, PEOPLE, 10 Sep. 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