Related Clues:

• Game opener?
• First X
• Uncontrolled contraction
• Small shake
• Foible
• First of three in a pencil/paper game
• It could be represented by an "X"
• Land movement
• Earthquake warning
• Persistent personal quirk
• ___-tac-toe
• First O?
• Quirky behavior
• The first O of O-O-O
• One might be verbal