Merriam-Webster Collegiate Dictionary - tic-tac-toe

 or tick-tack-toe  noun  Etymology: ~, former game in which players with eyes shut brought a pencil down on a slate marked with numbers and scored the number hit  Date: circa 1866 a game in which two players alternately put Xs and Os in compartments of a figure formed by two vertical lines crossing two horizontal lines and each tries to get a row of three Xs or three Os before the opponent does