Zugzwang is German for ‘compulsion to move’, pronounced tsoog-tsvahng; the term is used for a position in which whoever has the move would obtain a worse result than if it were the opponent’s turn to play.

The term is frequently used in chess. A player whose turn it is to move who has no move that does not worsen his position is said to be in zugzwang. Thus every move would make his position worse, and he would be better off if he could pass and not move.

In some literature a reciprocal zugzwang is called zugzwang and a one-sided zugzwang is called a squeeze. A position of mutual zugzwang in which either player would lose if it is their turn to move is called Trébuchet.

In game theory, it specifically means that it directly changes the outcome of the game from a win to a loss.