We found 21 dictionaries that define the word ugly duckling:

General (18 matching dictionaries)

1. ugly duckling: Longman Dictionary of Contemporary English
2. ugly duckling: Merriam-Webster
3. ugly duckling: Oxford Learner's Dictionaries
4. ugly duckling: American Heritage Dictionary of the English Language
5. ugly duckling: Collins English Dictionary
6. ugly duckling: Vocabulary.com
7. ugly duckling: Cambridge Advanced Learner's Dictionary
8. ugly duckling: Wiktionary
9. ugly duckling: The Wordsmyth English Dictionary-Thesaurus
10. ugly duckling: Infoplease Dictionary
11. ugly duckling: Dictionary.com
12. The Ugly Duckling (Pinkney book), The Ugly Duckling (animated film), The Ugly Duckling (audiobook), The Ugly Duckling (disambiguation), The Ugly Duckling (play), The Ugly Duckling, The ugly duckling, Ugly Duckling (TV series), Ugly Duckling (hip hop group), Ugly Duckling, Ugly duckling: Wikipedia, the Free Encyclopedia
13. ugly duckling: Rhymezone
14. ugly duckling: FreeDictionary.org
15. ugly duckling: Mnemonic Dictionary
16. ugly duckling: TheFreeDictionary.com

Computing (1 matching dictionary)

17. The Ugly Duckling, Ugly Duckling: Encyclopedia

Miscellaneous (1 matching dictionary)

18. ugly duckling: A Word A Day

Slang (1 matching dictionary)

19. Ugly duckling, ugly-duckling: Urban Dictionary

(Note: See ugly_ducklings as well.)

Definitions from Wiktionary (ugly duckling) ▸ noun:  (idiomatic) A young person who is ugly, but who is expected to become beautiful or handsome as they mature. Similar: ugly person, plug-ugly, ugly, mud duck, odd duck, lucky duckling, ruddy, fugly, ugly stick, pretty boy, more... Opposite: swan, beauty, transformation Phrases: The Ugly Duckling, Ugly duckling theorem, more... ▸ Words similar to ugly duckling ▸ Usage examples for ugly duckling ▸ Idioms related to ugly duckling ▸ Wikipedia articles (New!) ▸ Words that often appear near ugly duckling ▸ Rhymes of ugly duckling ▸ Invented words related to ugly duckling