Related Clues:

• Banned
• Off limits
• Rich dessert, to a dieter
• Putting regular gas in a diesel engine, e.g.
• Word of caution
• It's to be avoided
• It's taboo
• "--- ask!"
• It's a bad thing
• Cultural no-no
• Admonishing utterance
• "Cut it out!"
• "Cut it out"
• Admonishing word
• ''Please ___ Eat the Daisies''