Related Clues:

• Uncontrolled contraction
• Foible
• First of three in a pencil/paper game
• It could be represented by an "X"
• Uncorked, as champagne
• Persistent personal quirk
• ___-tac-toe
• First O?
• Quirky behavior
• Went first
• The first O of O-O-O
• Played first
• One might be verbal
• Involuntary contraction
• First O of O-O-O