We found 24 dictionaries that define the word sleeplessness:

General (16 matching dictionaries)

1. sleeplessness: Merriam-Webster
2. sleeplessness: Oxford Learner's Dictionaries
3. sleeplessness: Collins English Dictionary
4. sleeplessness: Vocabulary.com
5. Sleeplessness, sleeplessness: Wordnik
6. sleeplessness: Cambridge Advanced Learner's Dictionary
7. sleeplessness: Wiktionary
8. sleeplessness: Dictionary.com
9. Sleeplessness: Wikipedia, the Free Encyclopedia
10. sleeplessness: Rhymezone
11. sleeplessness: Webster's 1828 Dictionary
12. sleeplessness: FreeDictionary.org
13. sleeplessness: Mnemonic Dictionary
14. sleeplessness: TheFreeDictionary.com

Business (1 matching dictionary)

15. sleeplessness: Legal dictionary

Computing (1 matching dictionary)

16. sleeplessness: Encyclopedia

Medicine (6 matching dictionaries)

17. sleeplessness: Merriam-Webster Medical Dictionary
18. Sleeplessness: MedTerms.com Medical Dictionary
19. online medical dictionary (No longer online)
20. sleeplessness: Medical dictionary
21. University of Maryland Glossary of Medical Terms (No longer online)
22. Sleeplessness: Drug Medical Dictionary

(Note: See sleepless as well.)

Definitions from Wiktionary (sleeplessness) ▸ noun:  Lack of sleep; the property of being sleepless; the inability to sleep, insomnia. Similar: wakefulness, slumberlessness, insomnolency, unsleep, insomnolence, lack of sleep, bedlessness, sleep deprivation, wakelessness, lustlessness, more... Opposite: insomnia, insomniac Adjectives: chronic, persistent, obstinate, complete, great, much, occasional, own, nervous, total, long ▸ Words similar to sleeplessness ▸ Usage examples for sleeplessness ▸ Idioms related to sleeplessness ▸ Wikipedia articles (New!) ▸ Popular adjectives describing sleeplessness ▸ Words that often appear near sleeplessness ▸ Rhymes of sleeplessness ▸ Invented words related to sleeplessness