scum (sk?m)n.1. A filmy or frothy layer of matter that forms on the surface of a liquid or body of water or on a hard surface.2. The refuse or dross of molten metals.3. Refuse or worthless matter.4. Slang One, such as a person or an element of society, that is regarded as despicable or worthless.v. scummed, scum·ming, scums v.tr. To remove the scum from.v.intr. To become covered with scum.[Middle English, from Middle Dutch sch?m; see (s)keu- in Indo-European roots.]scum?mer n.scum?mi·ly adv.scum?mi·ness n.scum?my adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.scum (sk?m) n1. a layer of impure matter that forms on the surface of a liquid, often as the result of boiling or fermentation2. (Biology) the greenish film of algae and similar vegetation surface of a stagnant pond3. (Metallurgy) Also called: dross or scruff the skin of oxides or impurities on the surface of a molten metal4. waste matter5. a worthless person or group of peoplevb, scums, scumming or scummed6. (tr) to remove scum from7. (intr) rare to form a layer of or become covered with scum[C13: of Germanic origin; related to Old High German sc?m, Middle Dutch sch?m, Old French escume; see skim] ?scum?like adj ?scummer nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014scum (sk?m) n., v. scummed, scum?ming. n. 1. a. a film or layer of foul matter that forms on the surface of a liquid. b. a film of algae on still or stagnant water: pond scum. 2. refuse or offscourings. 3. a low, worthless person. 4. such persons collectively; dregs. v.i. 5. to form scum; become covered with scum. v.t. 6. to remove the scum from. [1200?50; Middle English scume