Source : Webster's Revised Unabridged Dictionary (1913)

Deflector \De*flect"or\, n. (Mech.)
   That which deflects, as a diaphragm in a furnace, or a cone
   in a lamp (to deflect and mingle air and gases and help
   combustion).

Source : WordNet®

deflector
     n : a device intended to turn aside the flow of something (water
         or air or smoke etc)