write in phrasal verb ( see also ↑ write )
1 . to write a letter to an organization to give an opinion, ask for information etc:
If you would like a copy of our fact sheet, please write in, enclosing a stamped addressed envelope.
write in to
And so I wrote in to Radio Brighton.
2 . write something ↔ in to write a piece of information in the space provided for it on a form or document:
Provide some space for students to write in their hobbies.
3 . write somebody ↔ in American English to add someone’s name to the official list on your voting form, to show that you want to vote for them:
The campaign to write in Johnson for governor failed.
⇨ ↑ write-in