I have to thank Frank Rich in the New York Times for introducing me to this delightful word. Meaning falsehood peddled as fact, it's simply perfect for the current political/social/entertainment climate in the USA.
The essential implication of truthiness is that it really doesn't matter if you are dealing with reality or fantasy – all that matters is that it sounds good and has a veneer of authenticity. Perhaps some people find this perfectly acceptable – much like cheating on tests – but it scares the willies out of me. "There are no facts, only interpretations" is a Nietzsche quote I most recently heard from Joss Ackland's lips as he portrayed Martin Heidigger during a recent BBC radio dramatisation, and will all know what happens when that sort of thinking loses any moral base.