[ sleep-lis ]
/ ˈslip lɪs /


without sleep: a sleepless night.
watchful; alert: sleepless devotion to duty.
always active: the sleepless ocean.

Origin of sleepless

late Middle English word dating back to 1375–1425; see origin at sleep, -less

Related forms

sleep·less·ly, adverbsleep·less·ness, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for sleepless

British Dictionary definitions for sleepless


/ (ˈsliːplɪs) /


without sleep or resta sleepless journey
unable to sleep
always watchful or alert
mainly poetic always active or movingthe sleepless tides

Derived Forms

sleeplessly, adverbsleeplessness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012