We found 26 dictionaries that define the word eightieth:

General (23 matching dictionaries)

1. eightieth: Merriam-Webster
2. eightieth: Oxford Learner's Dictionaries
3. eightieth: American Heritage Dictionary of the English Language
4. eightieth: Collins English Dictionary
5. eightieth: Vocabulary.com
6. Eightieth, eightieth: Wordnik
7. eightieth: Cambridge Advanced Learner's Dictionary
8. eightieth: Wiktionary
9. eightieth: Webster's New World College Dictionary, 4th Ed.
10. eightieth: The Wordsmyth English Dictionary-Thesaurus
11. eightieth: Infoplease Dictionary
12. Eightieth, eightieth: Dictionary.com
13. eightieth: Cambridge Essential American English Dictionary
14. Eightieth: Online Plain Text English Dictionary
15. eightieth: Webster's Revised Unabridged, 1913 Edition
16. eightieth: Rhymezone
17. Eightieth: AllWords.com Multi-Lingual Dictionary
18. eightieth: Webster's 1828 Dictionary
19. eightieth: FreeDictionary.org
20. eightieth: Mnemonic Dictionary
21. eightieth: TheFreeDictionary.com

Computing (1 matching dictionary)

22. eightieth: Encyclopedia

Medicine (1 matching dictionary)

23. online medical dictionary (No longer online)

Miscellaneous (1 matching dictionary)

24. eightieth: Idioms

(Note: See eighty as well.)

Definitions from Wiktionary (eightieth) ▸ adjective:  The ordinal form of the number eighty. ▸ noun:  The person or thing in the eightieth position. ▸ noun:  One of eighty equal parts of a whole. Similar: ordinal, 80th, eighty-first, eighty-eighth, eighty-oneth, eighty-fifth, eighty-second, eighty-third, sixtieth, eighty-fourth, more... Opposite: twentieth, ninetieth, seventieth Phrases: hundred and eightieth, more... ▸ Words similar to eightieth ▸ Usage examples for eightieth ▸ Idioms related to eightieth ▸ Wikipedia articles (New!) ▸ Popular adjectives describing eightieth ▸ Popular nouns described by eightieth ▸ Words that often appear near eightieth ▸ Rhymes of eightieth ▸ Invented words related to eightieth