skum

/S K AH0 M/
noun
  1. 1

    Obsolete spelling of scum (“surface impurities”). [(uncountable) A layer of impurities that accumulates at the surface of a liquid (especially molten metal or water).]

verb
  1. 1

    Obsolete spelling of scum (“remove surface impurities”). [To remove the layer of scum from (a liquid etc.).]