We found 10 dictionaries that define the word cool as a cucumber:

General (6 matching dictionaries)

1. cool as a cucumber: Oxford Learner's Dictionaries
2. cool as a cucumber: Collins English Dictionary
3. (as) cool as a cucumber: Cambridge Advanced Learner's Dictionary
4. cool as a cucumber: Wiktionary
5. Cool as a Cucumber: Dictionary of Phrase and Fable (1898)
6. cool as a cucumber: TheFreeDictionary.com

Computing (1 matching dictionary)

7. cool as a cucumber: Encyclopedia

Medicine (1 matching dictionary)

8. cool as a cucumber: Medical dictionary

Miscellaneous (1 matching dictionary)

9. cool as a cucumber: Idioms

Slang (1 matching dictionary)

10. cool as a cucumber: Urban Dictionary

Definitions from Wiktionary (cool as a cucumber) ▸ adjective:  (simile, informal) Calm and composed even in difficult or frustrating situations; self-possessed. Similar: calm as a cucumber, calm as a millpond, coolsome, Zen-like, calmish, coolish, chilled, smooth-brained, cold as ice, phlegmatic, more... Opposite: nervous, anxious, agitated, tense, uneasy Phrases: as cool as a cucumber, more... ▸ Words similar to cool as a cucumber ▸ Usage examples for cool as a cucumber ▸ Idioms related to cool as a cucumber ▸ Wikipedia articles (New!) ▸ Popular nouns described by cool as a cucumber ▸ Words that often appear near cool as a cucumber ▸ Rhymes of cool as a cucumber ▸ Invented words related to cool as a cucumber