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

Like most expectant parents, Briana Faucette heard the typical warnings about sleepless nights. — Roni Robbins, AJC.com, 20 July 2026

No, special teams coach Dave Toub shouldn’t spend sleepless nights scheming up how to improve his team’s field-goal defense for next season. — Jesse Newell, New York Times, 15 July 2026

Today, there are no more bodies left to bury, but those sleepless nights remain. — Bo Evans, CBS News, 2 July 2026

Fatigue, severe pain, heavy and irregular flow, sleepless nights on the bathroom floor. — Escher Walcott, PEOPLE, 16 June 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