According to New York City Photographer Avi Avnair who coined the term, a "Streetist" can be..
1. One who understands the mentality and psychology of residents of urban areas.
2. One who is makes a hobby of exploring sketchy urban areas.
3. One who is VERY streetwise, has a high level of street sense/logic.
4. One who has an appreciation for urban areas that have a worn or decayed look.
Jim, you can't walk Brownsville alone tonight. Bloods and Crip will maul your pussy ass. I'll call Jamal to walk with you, he's a REAL streetist.