Not sure that it means anything in particular. But as a succession of verbal images may be it aims to lead the listener towards their own interpretation. Is asking for the meaning a bit like asking Picasso what his paintings mean? Or perhaps I'm talking complete pseudo-intellectual bo**ocks too.

However, Dylan does seem to be good at this type of writing though it's hard to pin-point why. Many others tried it too, very few could match him. And despite being a massive Beatles fan, I think that their attempts pale drastically in comparison and verge, sometimes solidly, on the pretentious.