We found 12 dictionaries that define the word mightn't:

General (12 matching dictionaries)

1. mightn't: Merriam-Webster
2. mightn't: Oxford Learner's Dictionaries
3. mightn't: American Heritage Dictionary of the English Language
4. mightn't, mightn't: Collins English Dictionary
5. Mightn't, mightn't, mightnt: Wordnik
6. mightn't: Cambridge Advanced Learner's Dictionary
7. mightn't: Wiktionary
8. mightn't: Webster's New World College Dictionary, 4th Ed.
9. mightn't, mightnt: Dictionary.com
10. mightnt: Cambridge Essential American English Dictionary
11. Mightn't: Wikipedia, the Free Encyclopedia
12. mightn't: TheFreeDictionary.com

Definitions from Wiktionary (mightn't) ▸ verb:  (British) might not (negative auxiliary) Types: could, would, should, might, may, more... ▸ Words similar to mightn't ▸ Usage examples for mightn't ▸ Idioms related to mightn't ▸ Wikipedia articles (New!) ▸ Words that often appear near mightn't ▸ Rhymes of mightn't ▸ Invented words related to mightn't