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

This Black Friday, Grownsy offers practical, thoughtful tools designed to make everyday parenting a little easier—from helping with sleepless nights and messy kitchens to easing concerns about your baby’s comfort. —Matthew Kayser, USA Today, 12 Nov. 2025

Her troubles—sleepless nights, endless exhaustion—could simply be the result of young parenthood. —Shirley Li, The Atlantic, 6 Nov. 2025

Alice, a middling student at a state university in Oklahoma, drifts from adolescent confusion into sleepless paranoia. —The New Yorker, New Yorker, 3 Nov. 2025

With terrifying makeup that resembled the character’s sleepless, scarred face, the talk show host looked truly possessed with her blue nightgown and possessed demeanor. —Kate Hogan, PEOPLE, 30 Oct. 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