In chess, the term 'QUEEN' refers to a powerful piece that can move in any direction, horizontally, vertically, or diagonally. The QUEEN is represented by the letter 'Q' and is the most powerful piece on the board. The QUEEN is often used to protect the king, as it can move quickly and capture other pieces. The QUEEN is also used to attack the opponent's pieces, as it can move in multiple directions. The QUEEN is usually the last piece to be moved in a game of chess.