billboard

Short definition from Wiktionary

Noun

1. 1
   A very large outdoor sign, generally used for advertising.
2. 2
   A flat surface, such as a panel or fence, on which bills are posted; a bulletin board.
3. 3
   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.
4. 4
   An opening or closing portion of a program, often including credits and sponsors' names.
5. 5
   A sprite that always faces the screen, no matter which direction it is viewed from.

Verb

1. 1
   To advertise on a billboard.

Proper noun

1. 1
   The music charts published by Billboard magazine.