I'm not talking about the dictionary definition: an adjective meaning "of the city," derived from Latin urbanus and ultimately urbs, "city." Because that doesn't explain what "urban" is doing in this phrase, reproduced verbatim from a report I heard recently on my local public-radio station:
No, of course not. "Urban cities" may seem redundant, but the reporter had something else in mind. Increasingly over the last few decades, "urban" has acquired a secondary meaning: "dominated by a racial minority, usually African-American."