Related Clues:

• Verboten act
• Forbidden practice
• NASA failure
• Bad thing to do
• Slurping at the dinner table, e.g.
• Echoing taboo
• Forbidden act
• Futile
• Using metallic dishes in a microwave, e.g.
• Cell phone ring in a theater, e.g.
• It's frowned upon
• Smacking one's lips while eating, e.g.
• Forbidden action
• Elbows on the table, e.g.
• Roving eyes on an exam, e.g.