Skim coat

from The Collaborative International Dictionary of English v.0.48

Skim \Skim\, a.
   Contraction of {Skimming} and {Skimmed}.
   [1913 Webster]

   {Skim coat}, the final or finishing coat of plaster.

   {Skim colter}, a colter for paring off the surface of land.
      

   {Skim milk}, skimmed milk; milk from which the cream has been
      taken.
      [1913 Webster]