We found 23 dictionaries that define the word on the fly:

General (15 matching dictionaries)

1. on the fly: Longman Dictionary of Contemporary English
2. on the fly: Merriam-Webster
3. on the fly: Oxford Learner's Dictionaries
4. on the fly: Collins English Dictionary
5. on the fly: Vocabulary.com
6. on the fly: Wordnik
7. on-the-fly, on the fly: Wiktionary
8. On the fly, on the fly: Dictionary.com
9. On the Fly (album), On the Fly, On the fly: Wikipedia, the Free Encyclopedia
10. on the fly: Rhymezone
11. on the fly: FreeDictionary.org
12. on the fly: Mnemonic Dictionary
13. on the fly: TheFreeDictionary.com

Business (1 matching dictionary)

14. BusinessDictionary.com (No longer online)

Computing (2 matching dictionaries)

15. on-the-fly, on the fly: Netlingo
16. On-the-Fly, on the fly: Encyclopedia

Medicine (1 matching dictionary)

17. on the fly: Merriam-Webster Medical Dictionary

Miscellaneous (1 matching dictionary)

18. on the fly: Idioms

Slang (1 matching dictionary)

19. on the fly: Urban Dictionary

Sports (2 matching dictionaries)

20. Sports Terms (No longer online)
21. Hickok Sports Glossaries (No longer online)

Definitions from Wiktionary (on the fly) ▸ adverb:  (baseball, of the ball) While in the air, without having touched the ground. ▸ adverb:  (idiomatic) Spontaneously or extemporaneously; done as one goes, or during another activity. ▸ adverb:  (slang) On the move. Similar: aboard, the other way, overarm, short, Upfield, inbounds, en pointe, abroad, inside out, in-off, more... Opposite: pre-planned, premeditated, prearranged, preconceived, preordained Types: improvised, unplanned, extemporaneous, unrehearsed, ad-lib, more... Adjectives: back door, h, jack, ground, single, rainbow, side, base, screwball, outside, hold ▸ Words similar to on the fly ▸ Usage examples for on the fly ▸ Idioms related to on the fly ▸ Wikipedia articles (New!) ▸ Words that often appear near on the fly ▸ Rhymes of on the fly ▸ Invented words related to on the fly