Along the lines of ghetto-fabulous. Can be either a verb or an adjective. Usually used to describe something that is out of place, so to speak; not in an urban area.
ie. "Wow. Just look at that dumpy house. It is very 'urbantastic'" (referring to a house that is in a tidy suburb but looks like it belongs in the ghetto)
ie. If someone in your company was behaving loud and obnoxious and out of character, say, in a shopping mall. They are shouting loudly half way across the mall to a friend. You might say to them: "Umm, urbantastic much?" or "Wow - that was slightly urbantastic!"