When a player sees his position is hopeless, and ends the game before checkmate.

To concede loss of the game. A resignation is usually indicated by stopping the clocks, sometimes by offering a handshake, or by saying "I resign". A traditional way to resign was by tipping over one's king, but this is not done nowadays. It is common for a game to be resigned, rather than for it to end with checkmate, because experienced players can foresee the checkmate.