lou·ver /ˈluvɚ/
  天窗;屋頂窗;百葉窗;百葉窗板
  Lou·ver, Lou·vre  n.  Arch. A small lantern. See Lantern, 2 (a). [Written also lover, loover, lovery, and luffer.]
  Louver boards or Louver boarding, the sloping boards set to shed rainwater outward in openings which are to be left otherwise unfilled; as belfry windows, the openings of a louver, etc.
  Louver work, slatted work.
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  louver
       n : one of a set of parallel slats in a door or window to admit
           air and reject rain [syn: louvre, fin]