We found 46 dictionaries that define the word headache:

General (26 matching dictionaries)

1. headache: Merriam-Webster
2. headache: Oxford Learner's Dictionaries
3. headache: American Heritage Dictionary of the English Language
4. headache: Collins English Dictionary
5. headache: Vocabulary.com
6. Headache, headache: Wordnik
7. headache: Cambridge Advanced Learner's Dictionary
8. headache: Wiktionary
9. headache: Webster's New World College Dictionary, 4th Ed.
10. headache: The Wordsmyth English Dictionary-Thesaurus
11. headache: Infoplease Dictionary
12. headache: Dictionary.com
13. headache: Online Etymology Dictionary
14. headache: Cambridge Essential American English Dictionary
15. Headache (EP), Headache (Grimm), Headache (board game), Headache (disambiguation), Headache (game), Headache (journal), Headache (song), Headache: Wikipedia, the Free Encyclopedia
16. Headache: Online Plain Text English Dictionary
17. headache: Webster's Revised Unabridged, 1913 Edition
18. headache: Rhymezone
19. headache: AllWords.com Multi-Lingual Dictionary
20. headache: FreeDictionary.org
21. headache: Mnemonic Dictionary
22. headache: TheFreeDictionary.com
23. headache: Wikimedia Commons US English Pronunciations
24. headache: Longman Dictionary of Contemporary English

Art (1 matching dictionary)

25. Natural Magick (No longer online)

Computing (1 matching dictionary)

26. headache: Encyclopedia

Medicine (14 matching dictionaries)

27. headache: Merriam-Webster Medical Dictionary
28. Dorland's Illustrated Medical Dictionary (No longer online)
29. Headache: MedTerms.com Medical Dictionary
30. Medical Dictionary (No longer online)
31. Headache: MedFriendly Glossary
32. online medical dictionary (No longer online)
33. Specific Diseases/Disorders (No longer online)
34. Headache: MEDLINE plus Illustrated Medical Encyclopedia
35. Disorder Index (No longer online)
36. headache: Medical dictionary
37. Rudy's List of Archaic Medical Terms (No longer online)
38. University of Maryland Glossary of Medical Terms (No longer online)
39. Headache: Drug Medical Dictionary
40. Hyperdictionary (No longer online)

Miscellaneous (2 matching dictionaries)

41. Brilliant Dream Dictionary (No longer online)
42. headache: Idioms

Slang (1 matching dictionary)

43. headache: Green’s Dictionary of Slang

Tech (1 matching dictionary)

44. Oil and Gas Well Drilling and Servicing eTool (No longer online)

(Note: See headaches as well.)

Definitions from Wiktionary ( ) ▸ noun:  (medicine) A pain or ache in the head. ▸ noun:  (figurative) A nuisance or unpleasant problem. Similar: vexation, worry, concern, cephalalgia, head ache, headake, head, headwark, hornache, headwound, more... Opposite: relief, comfort, ease, tranquility, peace Types: migraine, cluster, tension, sinus, more... Phrases: cluster headache, migraine headache, tension headache, splitting headache, vascular headache, more... Adjectives: severe, chronic, bad, sick, migraine, frontal, type, violent, splitting, slight, intense Colors:     gray,     black,     red,     dark blue,     purple, more... ▸ Word origin ▸ Words similar to headache ▸ Usage examples for headache ▸ Idioms related to headache ▸ Wikipedia articles (New!) ▸ Popular adjectives describing headache ▸ Words that often appear near headache ▸ Rhymes of headache ▸ Invented words related to headache