Tic tac toe:
- 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.
- The player who succeeds in placing three of their marks in a horizontal, vertical, or diagonal row is the winner. It is a solved game, with a forced draw assuming best play from both players.There is no universally-agreed rule as to who plays first though.
- Tic-tac-toe is often played by young children who may not have discovered the optimal strategy.