We found 27 dictionaries that define the word smoking gun:

General (19 matching dictionaries)

1. smoking gun: Longman Dictionary of Contemporary English
2. smoking gun: Merriam-Webster
3. smoking gun: Oxford Learner's Dictionaries
4. smoking gun: American Heritage Dictionary of the English Language
5. smoking gun: Collins English Dictionary
6. smoking gun: Vocabulary.com
7. smoking-gun: Wordnik
8. smoking gun: Cambridge Advanced Learner's Dictionary
9. smoking-gun, smoking gun: Wiktionary
10. smoking gun: The Wordsmyth English Dictionary-Thesaurus
11. smoking gun: Infoplease Dictionary
12. smoking gun: Dictionary.com
13. Smoking Gun (TV series), Smoking Gun (album), Smoking Gun (disambiguation), Smoking Gun (song), Smoking Gun, Smoking gun (disambiguation), Smoking gun, The Smoking Gun (Ashes To Ashes), The Smoking Gun: Wikipedia, the Free Encyclopedia
14. smoking gun: Rhymezone
15. smoking gun: FreeDictionary.org
16. smoking gun: Mnemonic Dictionary
17. smoking gun: TheFreeDictionary.com

Business (3 matching dictionaries)

18. Everybody's Legal Dictionary (No longer online)
19. Smoking Gun: Investopedia
20. Smoking Gun: Financial dictionary

Medicine (1 matching dictionary)

21. smoking gun: Medical dictionary

Miscellaneous (1 matching dictionary)

22. the smoking gun: Idioms

Slang (3 matching dictionaries)

23. smoking gun: Green’s Dictionary of Slang
24. Smoking gun: Street Terms: Drugs and the Drug Trade
25. The Smoking Gun, smoking gun: Urban Dictionary

(Note: See smoking_guns as well.)

Definitions from Wiktionary (smoking gun) ▸ noun:  (idiomatic) Evidence, particularly of a crime, that is difficult or impossible to dispute. Similar: gunsmoke, ammunition, starting gun, shotgun, shotgun pleading, final nail in the coffin, gunpoint, gunning, smoke bomb, gunfire, more... Opposite: alibi, proof of innocence Phrases: The Smoking Gun, more... Adjectives: cocked, pokey, silenced, peak, shotted, wig, bassy, stick, double-barrelled, shotty, cannon ▸ Words similar to smoking gun ▸ Usage examples for smoking gun ▸ Idioms related to smoking gun ▸ Wikipedia articles (New!) ▸ Words that often appear near smoking gun ▸ Rhymes of smoking gun ▸ Invented words related to smoking gun