Related Clues:

• Library reminder
• Silencing sound
• "Stifle yourself!"
• "Quiet, please!"
• 'Zip it up!'
• Librarian's reprimand
• ''Keep it down!''
• Finger-to-lips syllable
• 'Hush up!'
• ''Silence!''
• "Be quiet!"
• ''Shut your mouth!''
• 'Zip your lips!'
• "Zip your lip!"
• Theater admonishment