sleepless

adjective

sleep·​less ˈslēp-ləs 

1

: not able to sleep

lay sleepless with fever

2

: affording no sleep

sleepless nights

3

: unceasingly active or operative

sleepless casinos

sleeplessly adverb

sleeplessness noun

Synonyms of sleepless

• wakeful
• awake

Examples of sleepless in a Sentence

He lay sleepless in bed.

Recent Examples on the Web

There have been plenty of sleepless nights for Betts so far this season. —Katie Woo, New York Times, 27 May 2026

This debt burden leads to higher stress and sleepless nights, and directly undermines the focus and efficiency of Americans in their prime working years. —Mary Moreland, Fortune, 17 May 2026

Here are my leftover thoughts on what should be a difficult slate as Patriots fans prepare for sleepless nights, an early morning and international travel, but zero holiday action. —Doug Kyed, Boston Herald, 15 May 2026

Fatigue, severe pain, heavy and irregular flow , sleepless nights on the bathroom floor . —Francie Ebert, NBC news, 14 May 2026

Word History

First Known Use

15th century, in the meaning defined at sense 1

Kids Definition

sleepless

adjective

sleep·​less ˈslē-pləs 

1

: not able to sleep

2

: marked by the absence of sleep

a sleepless night

3

: unceasingly alert or active

sleeplessly adverb

sleeplessness noun

Medical Definition

sleepless

adjective

sleep·​less ˈslē-pləs 

: not able to sleep : insomniac

sleeplessness noun