Wordnet 3.0
NOUN (1)
1. 
 a Muslim who represents the mystical dimension of Islam; 
 a Muslim who seeks direct experience of Allah; 
 mainly in Iran; 
ADJECTIVE (1)
1. 
 of or relating to the Sufis or to Sufism; 
The Collaborative International Dictionary of English v.0.48:
Sufi \Su"fi\, n. [From the name of a dynasty of Persian kings,
   Saf[imac], Safav[imac]; said to come from name
   Saf[imac]-ud-d[imac]n of an ancestor of the family, confused
   with s?f[imac] pious.]
   A title or surname of the king of Persia.
   [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Sufi \Su"fi\, n. [Ar. & Per. s?f[imac], wise, pious, devout.]
   One of a certain order of religious men in Persia. [Written
   also sofi.]
   [1913 Webster]
WordNet (r) 3.0 (2006):
Sufi
    adj 1: of or relating to the Sufis or to Sufism
    n 1: a Muslim who represents the mystical dimension of Islam; a
         Muslim who seeks direct experience of Allah; mainly in Iran