We found 11 dictionaries that define the word water off a duck's back:

General (6 matching dictionaries)

1. (like) water off a duck's back, water off a duck's back: Merriam-Webster
2. water off a duck's back: Oxford Learner's Dictionaries
3. water off a duck's back: Cambridge Advanced Learner's Dictionary
4. water off a duck's back, water off a ducks back: Dictionary.com
5. water off a duck's back: TheFreeDictionary.com
6. water off a duck's back: Wiktionary

Business (1 matching dictionary)

7. water off a duck's back: Legal dictionary

Computing (1 matching dictionary)

8. water off a duck's back: Encyclopedia

Medicine (1 matching dictionary)

9. water off a duck's back: Medical dictionary

Miscellaneous (1 matching dictionary)

10. water off a duck's back: Idioms

Slang (1 matching dictionary)

11. water off a duck's back: Urban Dictionary

Definitions from Wiktionary (water off a duck's back) ▸ noun:  Something potentially harmful or hurtful, such as criticism or insult, that nevertheless has no effect or impact on the target. Phrases: like water off a ducks back, more... ▸ Words similar to water off a duck's back ▸ Usage examples for water off a duck's back ▸ Idioms related to water off a duck's back ▸ Wikipedia articles (New!) ▸ Words that often appear near water off a duck's back ▸ Rhymes of water off a duck's back ▸ Invented words related to water off a duck's back