What does the word scum mean?

Usage examples for scum

  1. Young Lee, limp and dripping like a broken water- plant, was stretched upon the sofa, the green scum of the river upon his black hair, and a fringe of white foam upon his leaden- hued lips. – Round the Red Lamp Being Facts and Fancies of Medical Life by Arthur Conan Doyle
  2. She'd had some words, she said, with her mistress, and didn't propose to be treated like the scum of the earth by anybody. – The Prairie Mother by Arthur Stringer