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.
-I don't know Bob what is the number for 999?!?
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.
Girl: Suure baby.
Girl gives guy number.
Guy programs her in as (Ashley)999
"Yo man im horny lets call up some 999s."
"Who is this girl?? she looks slutty, oh thats just a 999"