Related Clues:

• Proscribed act
• Smoking while pumping gas, e.g.
• Fudge, to a dieter
• Thing we don't do
• Cake, on Atkins
• That which is not done
• Unwise act
• Double denial
• Thing to avoid
• Burping in public, e.g.
• Ill-advised move
• Off-limits act
• It just isn't done
• Non-starter
• Something proscribed