Islamic mysticism and Sufism are among important mental and cultural issues which have influenced Islamic – Iranian culture and Persian language and literature profusely. So the various dimensions of this mental and practical school must be revisited. One way to approach the subject and the end of this school as well as the history and content and changes is to examine the definitions which the pioneers and leading Sufis have provided. In this article, we have a critical look at these definitions in order to know this mental- practical school better and to clarify its hidden dimensions of that. To this end, in addition to referring to the leaders and followers of Sufism, their mental and practical framework will be illustrated.