Related Clues:

• Forbidden
• Canceled
• Emphatic denial
• Inoperative
• Transgression
• Taboo
• Banned act
• 'Forget it!'
• Off
• Faux pas
• It's outlawed
• Useless
• 'That's a ___!'
• Talking during a film, e.g.
• Thou-shalt-not