King (chess)
From Tardis Wiki, the free Doctor Who reference
The king was a chess piece used in games of chess. It was the one piece on the board the opposing player needed to capture in order to win the game, typically by forcing the player into checkmate. Each player controlled one each, coloured either black or white.
The Fourth Doctor had to move his king in a game of chess against K9 in order to stay in the game, having been put in Check. However, K9 claimed he would still win given the Doctor had fumbled capturing one of his bishops last turn. (TV: The Sun Makers)
