roughcast

1. A coarse plaster of lime, shells, and pebbles used for outside wall surfaces.
2. A rough preliminary model or form.

1. To plaster (a wall, for example) with roughcast.
2. To shape or work into a rough or preliminary form.

Species of external plastering or render composed of lime, sand, water, and small particles of gravel, pebbles, or crushed stones, thrown on to an undercoat of render before the latter has dried, also called pebble-dash, slapdash, or wetdash. See also harling.

The noun has 2 meanings:

Meaning #1: a coarse plaster for the surface of external walls

Meaning #2: a rough preliminary model

The verb roughcast has 3 meanings:

Meaning #1: shape roughly

Meaning #2: apply roughcast to (as of a wall)

Meaning #3: hew roughly, without finishing the surface
  Synonym: rough-hew