Did you know?

Click any word in a definition or example to find the entry for that word

opt in - definition and synonyms


What are red words?

90% of the time, speakers of English use just 7,500 words in speech and writing. These words appear in red, and are graded with stars. One-star words are frequent, two-star words are more frequent, and three-star words are the most frequent.



The thesaurus of synonyms and related words is fully integrated into the dictionary. Click on the thesaurus category heading under the button in an entry to see the synonyms and related words for that meaning.

phrasal verb [intransitive]
Word Forms
present tense
I/you/we/theyopt in
he/she/itopts in
present participleopting in
past tenseopted in
past participleopted in

or opt into

  1. to decide that you want to do something or be involved in something

    Members are given the choice to opt in.

    opt into something:

    The British government was reluctant to opt into such a system.

See also main entry: opt

sea lion

in an online conversation, repeatedly asking a person questions which suggest that you are interested in what they are talking about, but are actually intended to annoy them

BuzzWord Article

Open Dictionary


an electric skateboard

add a word


A must for anyone with an interest in the changing face of language. The Macmillan Dictionary blog explores English as it is spoken around the world today.

global English and language change from our blog
Macmillan learn live love play