I have never heard of that term, and it sounds overly fanciful. I'm guessing it is referring to the fact that nofollow links do not pass PageRank (like the PR evaporates and does not pass on). Hope this helps!
Not sure what you're referencing with "PR Evaporation" but as Ben indicated, "nofollow" links do not pass their trust or "link juice" to the site they point to and thus are thought to have no effect on a site's ranking.
In nofollow links link juice will not pass. In my opinion there is no nofollow page rank evaporation.
The nofollow links are not passing PR, so some of the PR will evaporate, but a part of it will still be distributed amongst the other outlinks.