The term 'OTHELLO PIECE' is a reference to the game of Othello, which is a two-player strategy board game. The pieces used in the game are known as discs, and each DISC has a black and white side. The objective of the game is to have the majority of your color discs on the board at the end of the game. The four-letter solution for this crossword is DISC, which is the name of the pieces used in the game of Othello.