Source : Webster's Revised Unabridged Dictionary (1913)

Dervish \Der"vish\, n.
   One of the fanatical followers of the Mahdi, in the Sudan.

Dervish \Der"vish\, Dervise \Der"vise\, Dervis \Der"vis\, n.
   [Per. derw[=e]sch, fr. OPer. derew to beg, ask alms: cf. F.
   derviche.]
   A Turkish or Persian monk, especially one who professes
   extreme poverty and leads an austere life.

Source : WordNet®

dervish
     n : an ascetic Muslim monk; a member of an order noted for
         devotional exercises involving bodily movements