The Collaborative International Dictionary of English v.0.48:

Landau \Lan"dau\, n. [From the town Ladau in Germany; cf. F.
   landau. See Land, Island.]
   A four-wheeled covered vehicle, the top of which is divided
   into two sections which can be let down, or thrown back, in
   such a manner as to make an open carriage. [Written also
   landaw.]
   [1913 Webster]