http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=mysticism
(WWWebster) gives
1 : the experience of mystical union or direct communion with ultimate
reality reported
by mystics
2 : the belief that direct knowledge of God, spiritual truth, or
ultimate reality can be
attained through subjective experience (as intuition or insight)
3 a : vague speculation : a belief without sound basis b : a theory
postulating the
possibility of direct and intuitive acquisition of ineffable knowledge
or power
Actually, I'd guess only a minority of theists are mystics, and it's
certainly the case that many mystics are agnostic or even
atheistic. Eg, me, who comes in as a believer in "direct
communion with ultimate reality", but not in God (though I do
have some sympathies with some of those who do).
Robin