From a discussion of "slipstream" on facebook:
I seem to remember that Sterling came up with "slipstream." Nowadays people call it "interstitial," though I don't, because I can neither spell nor pronounce it. Both terms come from within the science fiction community and apply (I think) to works that push at the traditional boundaries of SF. The words have nothing to do with fiction written outside SF. There is a lovely Halldor Laxness novel about a woman who is turned into a salmon and frozen in a glacier for decades, then recovered and turned back into a living woman. Not slipstream or inter-whatever, because those terms have no meaning in re Icelandic fiction of the first half of the 20th century. Calvino isn't slipstream. Nor is Borges. Lem might be, because he knew (and disliked) traditional SF.
I think these terms do have meaning within SF and may be useful in the field.
I don't like the terms personally, but I am not a critic. I also have a firm position on my own fiction. If I write it, it's science fiction or fantasy, dead center in the field.