We found 15 dictionaries that define the word opt in:

General (9 matching dictionaries)

1. opt in: Longman Dictionary of Contemporary English
2. opt in: Merriam-Webster
3. opt in: Collins English Dictionary
4. Opt-In, Opt-in, opt-in: Wordnik
5. opt-in, opt in: Wiktionary
6. Opt-in: Wikipedia, the Free Encyclopedia
7. opt in: TheFreeDictionary.com

Business (2 matching dictionaries)

8. BusinessDictionary.com (No longer online)
9. WebmasterWorld Webmaster and Search Engine Glossary (No longer online)

Computing (2 matching dictionaries)

10. opt-in: Netlingo
11. opt-in: Encyclopedia

Miscellaneous (1 matching dictionary)

12. opt in: Idioms

Slang (1 matching dictionary)

13. Opt in: Urban Dictionary

Definitions from Wiktionary (opt in) ▸ verb:  To choose to participate in something Similar: self-select, sign up, choose, get in on, choose up, join in, take, elect, take part, adopt, more... Opposite: opt out, decline, unsubscribe Phrases: opt in e mail, opt in email, more... Adjectives: liquidated, moratory, contracted, submissive, acquisite, safe, recipient, secure, acceptant, suscipient, allowed ▸ Words similar to opt in ▸ Usage examples for opt in ▸ Idioms related to opt in ▸ Wikipedia articles (New!) ▸ Words that often appear near opt in ▸ Rhymes of opt in ▸ Invented words related to opt in