The Collaborative International Dictionary of English v.0.48:

dump cart \dump cart\ n. (Railroads)
   same as dump car.

   Syn: dumping car, dumping cart, dump car. [PJC]

The Collaborative International Dictionary of English v.0.48:

Dump \Dump\ (d[u^]mp), v. t. [imp. & p. p. Dumped; p. pr. &
   vb. n. Dumping.] [OE. dumpen to throw down, fall down, cf.
   Icel. dumpa to thump, Dan. dumpe to fall suddenly, rush,
   dial. Sw. dimpa to fall down plump. Cf. Dump sadness.]
   1. To knock heavily; to stump. [Prov. Eng.] --Halliwell.
      [1913 Webster]

   2. To put or throw down with more or less of violence; hence,
      to unload from a cart by tilting it; as, to dump sand,
      coal, etc. [U.S.] --Bartlett.
      [1913 Webster]

   Dumping car or Dumping cart, a railway car, or a cart,
      the body of which can be tilted to empty the contents; --
      called also dump car, or dump cart.
      [1913 Webster]