So the (US) National Criminal Justice Reference Service defines gangs as "One common definition of a gang is a group of three or more individuals who engage in criminal activity and identify themselves with a common name or sign." I have to say, though, when I went to school (Criminology BA, 2001), we were specifically told that those conditions had to happen at the same time.

Like, if I'm hanging out with my knitting klatch, there are three or more of us who use a common name. But if three of us have been caught speeding within the last week, that really doesn't make us a rogue gang of knitters.

I would like to sit here with that mental image for a moment, though. I could make a mess with some metal needles.