A very large outdoor sign, generally used for advertising.
"The city council decided to repaint the faded billboard that overlooked the busy highway."
In plain English: A billboard is a large outdoor sign used to display advertisements for products, movies, or events along busy roads and streets.
"The bright billboard on the highway advertised the latest summer sale."
Usage: The term refers specifically to the physical structure itself rather than the advertisement displayed on it; use "ad" or "commercial" if you mean the message. In casual speech, people sometimes say "on a billboard," but technically one is in a billboard since the sign occupies the entire surface.
The music charts published by Billboard magazine.
"The singer saw her name rise to the top of the billboard after releasing her new hit single."
The word billboard is a straightforward compound formed from the words bill and board. It was first used to describe an advertisement printed on a large public notice board.