The Collaborative International Dictionary of English v.0.48:

Calash \Ca*lash"\, n. [F. cal[`e]che; of Slavonic origin; cf.
   Bohem. kolesa, Russ. koliaska calash, koleso, kolo, wheel.]
   1. A light carriage with low wheels, having a top or hood
      that can be raised or lowered, seats for inside, a
      separate seat for the driver, and often a movable front,
      so that it can be used as either an open or a closed
      carriage.
      [1913 Webster]

            The baroness in a calash capable of holding herself,
            her two children, and her servants.   --W. Irving.
      [1913 Webster]

   2. In Canada, a two-wheeled, one-seated vehicle, with a
      calash top, and the driver's seat elevated in front.
      [1913 Webster]

   3. A hood or top of a carriage which can be thrown back at
      pleasure.
      [1913 Webster]

   4. A hood, formerly worn by ladies, which could be drawn
      forward or thrown back like the top of a carriage.
      [1913 Webster]

WordNet (r) 3.0 (2006):

calash
    n 1: a woman's large folded hooped hood; worn in the 18th
         century [syn: calash, caleche]
    2: the folding hood of a horse-drawn carriage [syn: calash,
       caleche, calash top]