We found 18 dictionaries that define the word halcyon days:

General (11 matching dictionaries)

1. halcyon days: Merriam-Webster
2. halcyon days: Collins English Dictionary
3. halcyon days: Cambridge Advanced Learner's Dictionary
4. halcyon days: Wiktionary
5. halcyon days: Dictionary.com
6. Halcyon Days (BWO album), Halcyon Days (Bruce Hornsby album), Halcyon Days (Ellie Goulding album), Halcyon Days (Strawbs album), Halcyon Days (book), Halcyon Days (company), Halcyon Days (disambiguation), Halcyon Days, Halcyon days: Wikipedia, the Free Encyclopedia
7. Halcyon Days: Dictionary of Phrase and Fable (1898)
8. Halcyon days: Phrase Finder
9. halcyon days: Longman Dictionary of Contemporary English

Art (1 matching dictionary)

10. An Etymological Dictionary of Classical Mythology (No longer online)

Computing (1 matching dictionary)

11. halcyon days: Encyclopedia

Miscellaneous (1 matching dictionary)

12. the halcyon days: Idioms

Slang (1 matching dictionary)

13. Halcyon Days: Urban Dictionary

Tech (3 matching dictionaries)

14. Glossary of Meteorology (No longer online)
15. Lake and Water Word Glossary (No longer online)
16. SeaTalk Dictionary of English Nautical Language (No longer online)

Definitions from Wiktionary (halcyon days) ▸ noun:  Period of calm during the winter, when storms do not occur. ▸ noun:  (idiomatic) A period of calm, usually in the past and often nostalgic. Similar: calm, stormlessness, still, clock calm, lull, seasonlessness, chrysalism, horse latitudes, winterlessness, off-season, more... Opposite: troubled times, tumultuous era, chaotic period Adjectives: quiet, calm, halcyon, tranquil, dead calm, serene, peaceful, restful, placid, undisturbed, chill ▸ Words similar to halcyon days ▸ Usage examples for halcyon days ▸ Idioms related to halcyon days ▸ Wikipedia articles (New!) ▸ Words that often appear near halcyon days ▸ Rhymes of halcyon days ▸ Invented words related to halcyon days