What is a refined mysticism among certain classes of Mohammedans, particularly in Persia, who hold to a kind of pantheism and practice extreme asceticism in their lives. [Written also sofism.] called?

sufism — A refined mysticism among certain classes of Mohammedans, particularly in Persia, who hold to a kind of pantheism and practice extreme asceticism in their lives. [Written also sofism.]. (Webster's 1913.)