We found 13 dictionaries that define the word back-up:

General (7 matching dictionaries)

1. back-up: Collins English Dictionary
2. Back-Up, Back-up, back-up: Wordnik
3. back-up: Cambridge Advanced Learner's Dictionary
4. back-up: Wiktionary
5. Back-up: Wikipedia, the Free Encyclopedia
6. Back-Up: American-Britih Dictionary
7. back-up: TheFreeDictionary.com

Art (1 matching dictionary)

8. Technical Glossary of Theatre Terms (No longer online)

Business (2 matching dictionaries)

9. Back-up: bizterms.net
10. back-up: Legal dictionary

Computing (1 matching dictionary)

11. Back-up: Encyclopedia

Medicine (1 matching dictionary)

12. Back-up: Medical dictionary

Slang (1 matching dictionary)

13. back-up: Urban Dictionary

Definitions from Wiktionary (Back-up) ▸ adjective:  Alternative form of backup [Standby, reserve or extra.] ▸ noun:  Alternative form of backup [A reserve or substitute.] Similar: back-assward, backasswards, upsidedown, behind-the-scenes, on-hand, stop-gap, piggy-back, bassackwards, off-guard, sway-backed, more... Opposite: primary, forefront, lead, main, front Types: cloud, external hard drive, flash drive, more... Phrases: The Back-up Plan, Back-up beeper, Back-up partner, more... Colors:     gray,     black,     white,     silver,     teal, more... ▸ Words similar to back-up ▸ Usage examples for back-up ▸ Idioms related to back-up ▸ Wikipedia articles (New!) ▸ Popular adjectives describing back-up ▸ Popular nouns described by back-up ▸ Words that often appear near back-up ▸ Rhymes of back-up ▸ Invented words related to back-up