noun

• (dated) A flat surface, such as a panel or fence, on which bills are posted; a bulletin board.
  "When a show leaves New York, it carries posters wherewith to embellish each fence and bill board in the land [...]"
• (nautical) A piece of thick plank, armed with iron plates, and fixed on the bow or fore-channels of a vessel, for the bill or fluke of the anchor to rest on.
• (television, radio) An opening or closing portion of a program, often including credits and sponsors' names.
  "The closing billboard features Como as the spokesman."
• (computer graphics) A sprite that always faces the screen, no matter which direction it is viewed from.

verb

• (transitive) To advertise on a billboard.
  "The upcoming concert was billboarded all over the city."