Checkmate

Checkmate was the winning move in chess.

According to Marco Polo, it came from the phrase "Shāh Māt", or "the king is dead". (TV: "The Singing Sands")

K9 expressed he could put the Fourth Doctor in checkmate within six moves during their game of chess. (TV: The Sun Makers)

Artie Maitland was put in checkmate by Porridge in their game of chess, having fallen for a "Fool's mate". The Eleventh Doctor later claimed he could put Mr Clever into checkmate in three moves during their game. However, he did not mean chess, but them actually fighting for control of his mind outside of the game, subsequently doing so by using a hand pulse on the Cyber-Planner's circuits. (TV: Nightmare in Silver)