Cityspeak is the "street" language of the denizens in the Blade Runner world .
That gibberish he talked was Cityspeak, gutter talk, a mishmash of Japanese, Spanish, German, what have you. I didn’t really need a translator. I knew the lingo, every good cop did. But I wasn’t going to make it easier for him.
Much of the Cityspeak used in the film was devised by Edward James Olmos, during background research for his character (Gaff).
In addition to Japanese, Spanish, and German, Olmos also used elements of Hungarian, Chinese, and French. Other street dialog in the film uses Korean.