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

• wakeful
• awake

Examples of sleepless in a Sentence

He lay sleepless in bed.

Recent Examples on the Web

Every decision that led to an expansion of Live Nation’s business remit was almost certainly preceded by enormous amounts of uncertainty and sleepless nights. —John Tamny, Forbes.com, 2 Sep. 2025

What happened next has caused Cadrez multiple sleepless nights. —Troy Renck, Denver Post, 1 Sep. 2025

His sleepless stare has amused viewers, many of whom said the dog's face perfectly captured the feeling of trying to enjoy a holiday under less-than-ideal conditions. —Melissa Fleur Afshar, MSNBC Newsweek, 25 Aug. 2025

Fatigue, severe pain, heavy and irregular flow, sleepless nights on the bathroom floor. —Toria Sheffield, People.com, 18 Aug. 2025

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