Definition: worthless or dangerous material that should be removed
Usage: there were impurities in the water
Similar words: waste, waste material, waste matter, waste product
Definition: any materials unused and rejected as worthless or unwanted
Usage: they collect the waste once a week; much of the waste material is carried off in the sewers
Definition: the scum formed by oxidation at the surface of molten metals
Similar words: scum
Definition: a film of impurities or vegetation that can form on the surface of a liquid