Deed to avoid

• Something that's out of bounds: Hyph
• Off-limits thing
• Ill-advised move
• It's the wrong thing to do
• Ice cream and cake, when dieting
• Fudge, to a dieter
• Unacceptable action: Hyph
• Something taboo
• Pitcher's gem, in baseball lingo

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