Check (chess)
From Tardis Wiki, the free Doctor Who reference
Check was a condition in chess where a player's king piece was under threat and would be captured next turn if not moved to safety. Failure to protect the King when in check would result in a Checkmate.
The Fourth Doctor's king piece was checked in a game of chess against K9. The Doctor managed to save his king, but K9 still persisted the Doctor would lose in six moves. (TV: The Sun Makers)
