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". Mr Clever declared checkmate in five moves if the Eleventh Doctor sacrificed his queen piece rather than take his bishop during their game. The Doctor agreed, claiming sacrificing the queen meant he could put Mr Clever into checkmate in three moves. 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)