Source : Webster's Revised Unabridged Dictionary (1913)

Vizier \Viz"ier\, n. [Ar. wez[=i]r, waz[=i]r, properly, a bearer
   of burdens, a porter, from wazara to bear a burden: cf. F.
   vizir, visir. Cf. {Alguazil}.]
   A councilor of state; a high executive officer in Turkey and
   other Oriental countries. [Written also {visier}, {vizir},
   and {vizer}.]

   {Grand vizier}, the chief minister of the Turkish empire; --
      called also {vizier-azem}.

Source : WordNet®

vizier
     n : a high official in a Muslim government (especially in the
         Ottoman Empire)