This mean snitching.
Also can be said as "triple nine'in"

The number for the emergency services i.e the police, A&E, fire service.
Often pranked from public telephones by children and adults alike for a quick laugh at someone elses expence.
Also often used for the wrong reasons like 999 was dialed because someones curry was too hot.

Some think that 999 is the true number of the beast because john of the bible dreamed the numbers 666 according to the book of revelations but numbers are dreamt upside down.

(pronoun) a band based in England, of early punk roots in the seventies.

Term referring A Booty call.
A one night stand.
When you get a girls number at a club or a party and have little intent of calling her the next day.
A hoodrat hoe.
A hookup.

The number geeks use to stand for infinity. Basically, it comes from many video games which don't exceed three digits in certain critical categories like hit points, energy, damage, …etc. So if you are at 999, you have reached the absolute pinnacle of achievement, and your powers are nigh godlike. Therefore, we can use 999 to substitute for and denote all other superlatives.

this is the "BLOOD" call for snitchin; WARNING: IF YOU ARE NOT A BLOOD OR DON'T UNDERSTAND gangbangin' BECAREFUL WHEN SAYING THIS