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

Enter the Mirakuru Pillow for back and side sleepers, which features six multidirectional air chambers that gently inflate and deflate to shift your head's position throughout the night. —New Atlas, 20 Apr. 2026

These cooling sheets and bedding essentials are lightweight and breathable enough to keep hot sleepers comfortable on even the hottest Southern nights. —Caley Sturgill, Southern Living, 19 Apr. 2026

There’s plenty of spring-friendly bedding worth shopping, too, like this pretty comforter with feminine ruffle details or a cooling blanket that thousands of hot sleepers swear by. —Stephanie Osmanski, Better Homes & Gardens, 17 Apr. 2026

Irregular sleepers showed a 20 to 88% higher all-cause mortality risk independent of duration. —Allison Palmer, Fort Worth Star-Telegram, 17 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