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

Thousands of opinions, sleepless nights and countless responsibilities that come with being a CEO – all included. —Jesse Whittock, Deadline, 3 Feb. 2026

Left unchecked, those feelings can worsen into sleepless nights, a loss of appetite, inability to focus, impaired relationships, depression and even physical illness. —Hunter Boyce, AJC.com, 27 Jan. 2026

Continue reading … SOUND OF MADNESS – Mystery hum rattles American city as residents report sleepless nights and rising fear. —FOXNews.com, 23 Jan. 2026

Countless athletic coaches have sleepless nights (and maybe lost their jobs) because of a mismatch of purpose and determination. —Neil Senturia, San Diego Union-Tribune, 12 Jan. 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