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

Saatva mattresses are highly recommended for people with back and joint pain, as well as side sleepers. —Alora Bopray, USA Today, 10 Apr. 2026

My favorite sleeper is Iowa’s Mark Gronowski. —Nick Baumgardner, New York Times, 10 Apr. 2026

The Sleep Foundation calls it the foundational move for new back sleepers. —Allison Palmer, Charlotte Observer, 9 Apr. 2026

This takes pressure off the lower back and is the Sleep Foundation’s recommended first move for new back sleepers. —Allison Palmer, Miami Herald, 9 Apr. 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