1. a four-wheeled covered carriage with the top in two sections, either of which can be lowered independently. 2. a former style of automobile with a top whose back could be folded down.
But here's the 1979 Chevrolet Caprice Landau. Hmmm. Could it be GM or Chevy misappropriated a catchy, marketable, automotive-ish term to describe cars where the roof––neither the front or back–– could be folded?
Chevrolet is not alone in this. Chryslers were badged with "Landau" for one as were other makes or models that have since disappeared. Ford Company used the term for the Lincoln once upon a time, I believe.
"Landau" has lost its clout in modern car badging and trim versions. Now we respond to GTO, GTX, STS, or Taurus, Fury, Monza, Sierra, Santa Fe, Outback.