Definition of Poster

Noun: poster pow-stu(r)

A sign posted in a public place as an advertisement
"a poster advertised the coming attractions";
- posting, placard, notice, bill, card
Someone who pastes up bills or placards on walls or billboards
- bill poster, bill sticker
Someone who sends a message to an internet discussion forum, blog, newsgroup, mailing list, etc.
[archaic] A horse kept at an inn or post house for use by mail carriers or for rent to travellers
- post horse, post-horse