Is displaying your stomach a new type of thug posturing?

I run every day in this subdivision behind my house. It’s a rather nice neighborhood, but it is populated by 4 or 5 teenage hoodrat wannabees who I occasionally see out and about, but they’ve never paid much mind to me until today.

I had just finished a sprint and I was reducing my pace to a jog when a car whooshed by me with the distinct smell of mary j wafting from the windows. The car stopped in a driveway a dozen yards ahead of me, and two of the aforementioned hoodrats stepped out and aggressively and immediately flipped up their shirts and held them up to display their stomachs. They both grinned widely, their faux grills glinting in the afternoon sun. One of them said “what it do, playa.”

I kept jogging, and when I got home, I began to ponder the peculiarity of this display. I realized that I had seen a similar display with a thuggish student I go to school with. Google returns no results, and I’m wondering what this means. Is it a greeting? A challenge? Enlighten me, Fluther.