Double-dipping, for example

• Thing to avoid doing
• Something never to be done
• Bad thing to do
• Taboo that may be worthy of a time-out
• Something that's not allowed: Hyph
• Thou-shalt-not
• This makes a censor tenser
• Dessert, to dieters
• It's strictly taboo

Wiktionary Word definitions in Wiktionary
n. (alternative spelling of no-no English)