from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Marked by a lack of sleep: a sleepless night.
- adj. Unable to sleep.
- adj. Always alert or active; never resting: a sleepless district of the city.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Characterized by an absence of sleep.
from the GNU version of the Collaborative International Dictionary of English
- adj. Having no sleep; wakeful.
- adj. Having no rest; perpetually agitated.
from The Century Dictionary and Cyclopedia
- Being without sleep; wakeful.
- Constantly watchful; vigilant: as, the sleepless eye of justice.
- Restless; continually disturbed or agitated.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. always watchful
- adj. experiencing or accompanied by sleeplessness
sleep + -less (Wiktionary)