Related Clues:

• Little jerk
• Peculiarity
• Involuntary muscular contraction
• Game opener?
• First X
• Uncontrolled contraction
• Foible
• First of three in a pencil/paper game
• It could be represented by an "X"
• Persistent personal quirk
• ___-tac-toe
• First O?
• Quirky behavior
• The first O of O-O-O
• One might be verbal