/ ˈpəʊstə(r); NAmE ˈpoʊ-/ noun
1.
a large notice, often with a picture on it, that is put in a public place to advertise sth
SYN placard :
election posters
a poster campaign (= an attempt to educate people about sth by using posters )
2.
a large picture that is printed on paper and put on a wall as decoration :
posters of her favourite pop stars
3.
a person who posts a message on a message board (= a place on a website where people can read or write messages)