I think the closest analogue to a bounced visit is a window shopper: they take a glance at your site as they're walking by, don't see anything that catches their eye, and move along. Of course, the analogy isn't quite the same because the "boundaries" feel different--a window shopper never enters your shop, but a bounced visitor does enter your site. Perhaps you can imagine that the "boundaries" of your shop includes the storefront and the little area of street outside, where you may set up a sign. Similarly, you may not consider someone "in" your site until they click past the shiny welcome mat.
In any case, the analogy is useful because your tactics as a site/shop owner are similar: you have someone's two-second glance at your pretty facade as they walk past to pique their interest and convert them into a browser. And once they're in, you still have to convert them to a buyer.
In Google Analytics, the referring URL is overridden by the contents of utm_source if it is present. In addition, changing the utm_medium means that the new source value won't show up in the Referring Sites report with the rest of the referring traffic. If you were looking in GA, you wouldn't be able to figure out where this traffic was coming from, and your search traffic will be inflated.
Of course, if it's your site, mess with your data all you want. Just be sure to let your analyst know, so he doesn't spend all week trying to find the inexplicable jump in traffic from this new search engine named "hn."
In any case, the analogy is useful because your tactics as a site/shop owner are similar: you have someone's two-second glance at your pretty facade as they walk past to pique their interest and convert them into a browser. And once they're in, you still have to convert them to a buyer.