Unlike insanity, which is simply a lack of sanity, outsanity is the complete opposite of sanity. Imagine going all the way through insanity and coming out on the other end, discworld-like, in a state that is so silly and weird and zany that there is no other way to describe it other that being completely outsane; a sort of state where your sanity is racing down a fifth-dimension street with a soapbox parade in tow, shouting 'I am the emperor of Sicily! I am nighthoover! Fear me! FEAR ME!' - imagine that, if you can, and you might get an idea of what outsanity is like. But you have to be there to know it.
A: What the hell is that? Are you mad?
B: Mad? Me? Oh nonono, my dear... I'm outsane. Muahahahaha!