Eating with one's elbows on the table, e.g

• Toddler's taboo
• Tyke's transgression
• Fudge, to a dieter
• Thing a small child shouldn't do: Hyph
• ''___ Nanette''
• It's a bad thing
• Reprimand to tots
• Interdiction, to an infant
• One of seven Nolan Ryan gems, informally

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