Look up buck in Wiktionary, the free dictionary.
&sq=Albert Einstein&lang=en&file=File:Dealer_button_chip_%26_playing_cards.JPG)
In poker, the buck or dealer button is a marker used to indicate the player who is dealing or, in casino games with a house dealer, the player who acts last on that deal (who would be the dealer in a home game). The term button is also used for a variety of plastic discs, or lammers, used by casinos to mark the status of players.