deflector

from WordNet (r) 3.0 (2006)

deflector
    n 1: a device intended to turn aside the flow of something
         (water or air or smoke etc)

from The Collaborative International Dictionary of English v.0.48

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).
   [1913 Webster]