The term 'Diagonal-Moving Chesspiece' refers to the BISHOP, a 6-letter chess piece that moves diagonally across the board. The BISHOP is one of the six pieces in a standard game of chess, and it can move any number of squares diagonally in any direction, as long as it does not jump over other pieces. It is also important to note that each player has two Bishops, one on the white squares and one on the black squares.