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

After enduring a sleepless night while the settlers slept on their library floor, the Khalidi family regrouped in the morning. —Ryan Byrnes, Literary Hub, 7 Oct. 2025

Members of the Afghan diaspora spent hours, and sleepless nights, trying to call and text relatives, friends and colleagues back home. —Hilary Whiteman, CNN Money, 3 Oct. 2025

The more complex, ugly feelings start to bleed into sleepless ruminations about her life. —Brittany Spanos, Rolling Stone, 26 Sep. 2025

Still, being a winner of such a large prize has left the Missouri man in disbelief — and lottery officials said he's had quite a few sleepless nights. —Abigail Adams, PEOPLE, 25 Sep. 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