We get the word mystic from a Greek root that means "mystery." A mystic is a person who is "introduced into the mysteries." Broadly speaking, all Christians are mystics. We believe that by faith we are initiated into the mysteries of Christ's death and resurrection. But most Christians are not mystics in the technical sense because we have yet to penetrate the Christian mysteries in depth. That's what sets a true mystic apart from the crowd. Mystics enjoy a special closeness to God. They get rid of all the clutter in their hearts to make more room for God.
from the book "Mystics & Miracles: True Stories of Lives Touched by God" by Bert Ghezzi p. xi