<p><strong>Noun</strong></p><ul><li>a film or layer of foul or extraneous matter that forms on the surface of a liquid.</li><li>refuse or offscourings.</li><li>a low, worthless, or evil person.</li><li>such persons collectively; riffraff; dregs.</li><li>scoria.</li></ul><p><strong>Verb</strong></p><ul><li>(used with object) to remove the scum from.</li><li>to remove as scum.</li><li>(used without object) to form scum; become covered with scum.</li></ul>