Blatherskite is silly, babbling speech that doesn't really mean anything. If you know someone who talks just to hear his own voice, you can call what he says blatherskite.
The person you're sitting beside on a long flight might spout blatherskite the whole time, or you might gradually realize a political speech is nothing but blatherskite. In both cases, the words don't really mean much, and there are far too many of them. Blatherskite became US slang in the early 19th century from bletherskate, or "foolish fellow," featured in the Scottish song "Maggie Lauder," which was popular with Continental soldiers during the American Revolution.