We found 13 dictionaries that define the word on the off chance:

General (9 matching dictionaries)

1. on the off chance: Longman Dictionary of Contemporary English
2. on the off chance: Merriam-Webster
3. on the off-chance, on the off-chance, on the off chance: Collins English Dictionary
4. on the off chance: Cambridge Advanced Learner's Dictionary
5. on the off chance: Wiktionary
6. on the off chance: Dictionary.com
7. on the off chance: TheFreeDictionary.com

Business (1 matching dictionary)

8. on the off chance: Legal dictionary

Computing (1 matching dictionary)

9. on the off chance: Encyclopedia

Medicine (1 matching dictionary)

10. on the off chance: Medical dictionary

Miscellaneous (1 matching dictionary)

11. on the off-chance, on the off chance: Idioms

Definitions from Wiktionary (on the off chance) ▸ adverb:  Hoping that (something is the case), even if it is unlikely. Similar: just in case, if anything, on spec, just incase, what if, if, as and when, worst comes to worst, prob, poss., Prob., more... ▸ Words similar to on the off chance ▸ Usage examples for on the off chance ▸ Idioms related to on the off chance ▸ Wikipedia articles (New!) ▸ Words that often appear near on the off chance ▸ Rhymes of on the off chance ▸ Invented words related to on the off chance