The Collaborative International Dictionary of English v.0.48:

Platband \Plat"band`\, n. [F. plate-bande; plat, plate, flat,
   level + bande a band.]
   1. A border of flowers in a garden, along a wall or a
      parterre; hence, a border.
      [1913 Webster]

   2. (Arch.)
      (a) A flat molding, or group of moldings, the width of
          which much exceeds its projection, as the face of an
          architrave.
      (b) A list or fillet between the flutings of a column.
          [1913 Webster]