Related Clues:

• What twitch regularly shows?
• With 40- and 43-Across, game that's been played in each of this puzzle's corners
• Rapid eye blinking, e.g
• ___ tac toe
• ''___ Tac Dough''
• ''___ Tac Dough'' (quiz show)
• ___-Tac-Toe
• First word of a game with X's and O's
• ___ Tac Toe
• First X or O, in a game
• First of three-in-a-row, in a game
• First O of OOO
• Nervous motion
• Was on first
• Idiosyncratic contraction