What is the meaning of Billboard?

A very large outdoor sign, generally used for advertising.

A flat surface, such as a panel or fence, on which bills are posted; a bulletin board.

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.

A sprite that always faces the screen, no matter which direction it is viewed from.

To advertise on a billboard.

billboard (large advertisement along side of highway)

Alternative spelling of bilbord

Source: wiktionary.org