Related Clues:

• Start of a simple game
• First X, maybe
• ''Veil'' author Woodward
• Muscle spasm
• Sudden contraction
• Sign of nerves
• Muscle contraction
• Twinge
• Involuntary twitch
• Recurrent twitch
• Head motion
• Eccentricity
• An X could represent it
• Little jerk
• Peculiarity