Related Clues:
- Thumbs-down at NASA
- Burping in public, e.g.
- Like a scrubbed space mission
- Ill-advised move
- Canceled, to 69-Across
- Off-limits act
- It just isn't done
- Non-starter
- Scrubbed, NASA-style
- Something proscribed
- Banned behavior
- Prohibited behavior
- Admonishment to junior
- Bit of naughtiness
- Admonition to Nanette?