What is Checkmate ?
Checkmate is (noun) (in chess) a situation at the end of a game where the king cannot move That’s checkmate!(verb) 1. (in chess) to put your opponent’s king in a position from which he cannot escape She managed to checkmate me for the second game running. (NOTE: also shortened simply to mate) 2. to put an opponent into an impossible situation If the judiciary manages to checkmate the president, he will have to resign.
source: Easier English, Student Dictionary Upper Intermediate Level