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

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

My heart broke at the thought that daddy wasn’t coming home for two little kids, and that poor mommy would have to try to explain what happened, endure sleepless nights, and try to move on with her family torn apart. —Matt Fleming, Oc Register, 20 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