A mystic is someone who has a personal, unmediated, felt sense of God. It’s not a set of ideas or beliefs, and it is not a hopefulness or even a general openness. It is deep experience that cannot be explained through reference to thought or emotion, and it is almost always unexplainable through language. But it comes with an utter certainty that a direct connection to spirit has been formed. No one can truly share it, but nothing can take it away. I think William James came very close in categorizing it as ineffable, noetic, transient, and passive (explanations of those terms are here: http://www.bodysoulandspirit.net/mystical_experiences/learn/experts_define/james.shtml). Those are the conditions that surround it, though they do not capture the nature of the mystical experience itself, which feels as if it comes from a different realm, one which cannot be explained by reference to anything else we know. In my experience, people who truly live in the mystic realm very rarely share their specific experiences, and they almost never try to generalize them.
Denise Wilbur