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Noun:To refer to a dangerous place or situation that should be avoided or at least only be entered with significant backup.

The slang originates from the UK Police emergency "Code Zero" the slang is particularly suitable for urban centres that are infested with ronkers.
If you were meeting for a pint in Bradford City centre before 6pm, a suitable sentence would be:

"Let's grab a beer at the Shoulder of Mutton before Code Zero”

If you were on a night out and you found yourself outside a rough nightclub that attracted the chav and ronker crew and you wanted to suggest another venue, a suitable phrase would be:

“There’s no way I’m going in there it’s Code Zero”
by HeadStAtEUK! March 25, 2011
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