We found 17 dictionaries that define the word S/N:

General (7 matching dictionaries)

1. S/N: Vocabulary.com
2. S/N: Webster's New World College Dictionary, 4th Ed.
3. s/n: Dictionary.com
4. S/n: Rhymezone
5. s/n: FreeDictionary.org
6. s/n: Mnemonic Dictionary
7. S/N: TheFreeDictionary.com

Business (1 matching dictionary)

8. Glossary of Trade and Shipping Terms (No longer online)

Computing (2 matching dictionaries)

9. BABEL: Computer Oriented Abbreviations and Acronyms (No longer online)
10. S/N: Encyclopedia

Miscellaneous (2 matching dictionaries)

11. S/N: Acronym Finder
12. AbbreviationZ (No longer online)

Slang (1 matching dictionary)

13. s/n: Urban Dictionary

Tech (4 matching dictionaries)

14. S/N: GEOGRAPHIC INFORMATION SYSTEMS, CARTOGRAPHY, AND REMOTE SENSING
15. DOD Dictionary of Military Terms: Joint Acronyms and Abbreviations (No longer online)
16. Dictionary for Avionics (No longer online)
17. Rane Professional Audio Reference (No longer online)

(Note: See s/ns as well.)

Definitions from WordNet (S/n) ▸ noun:  the ratio of signal intensity to noise intensity Similar: signal-to-noise, signal-to-noise ratio, signal/noise, signal/noise ratio, poles apart, complex geometry, contact geometry, zero in, square away, group theory, more... Opposite: y/n, yes/no Phrases: s/n ratio, more... ▸ Words similar to S/N ▸ Usage examples for S/N ▸ Idioms related to S/N ▸ Wikipedia articles (New!) ▸ Popular adjectives describing S/N ▸ Words that often appear near S/N ▸ Rhymes of S/N ▸ Invented words related to S/N