We found 24 dictionaries that define the word opt out:

General (17 matching dictionaries)

1. opt out: Longman Dictionary of Contemporary English
2. opt out: Merriam-Webster
3. opt-out, opt out: Oxford Learner's Dictionaries
4. opt-out, opt-out, opt out: Collins English Dictionary
5. opt out: Vocabulary.com
6. Opt-Out, Opt-out, opt-out: Wordnik
7. opt-out, opt out: Cambridge Advanced Learner's Dictionary
8. opt-out, opt out: Wiktionary
9. opt-out, opt out: Dictionary.com
10. Opt-out, Opt-out (politics), Opt out: Wikipedia, the Free Encyclopedia
11. opt out: Rhymezone
12. opt-out: AllWords.com Multi-Lingual Dictionary
13. opt out: FreeDictionary.org
14. opt out: Mnemonic Dictionary
15. opt-out, opt out: TheFreeDictionary.com

Business (2 matching dictionaries)

16. BusinessDictionary.com (No longer online)
17. WebmasterWorld Webmaster and Search Engine Glossary (No longer online)

Computing (3 matching dictionaries)

18. opt-out: Netlingo
19. Marketing Terms.com - Internet Marketing Dictionary (No longer online)
20. opt-out: Encyclopedia

Miscellaneous (1 matching dictionary)

21. opt out: Idioms

Slang (1 matching dictionary)

22. opt out: Urban Dictionary

(Note: See opt_outs as well.)

Definitions from Wiktionary (opt out) ▸ verb:  To choose not to participate in something. Similar: cop out, drop out, pull the pin, unchoose, sit out, deselect, decline, unvolunteer, abstain, back out, more... Opposite: opt in, enroll, subscribe Adjectives: desert, mittent, exempt, abstract, term, quit, part, shot, put out, obviate, void ▸ Words similar to opt out ▸ Usage examples for opt out ▸ Idioms related to opt out ▸ Wikipedia articles (New!) ▸ Words that often appear near opt out ▸ Rhymes of opt out ▸ Invented words related to opt out