The extraneous matter or impurities which rise to the surface of liquids in boiling or fermentation, or which form on the surface by other means; also, the scoria of metals in a molten state; dross.
- A filmy layer of extraneous or impure matter that forms on or rises to the surface of a liquid or body of water.
- The refuse or dross of molten metals.
- Refuse or worthless matter.
- Slang One, such as a person or an element of society, that is regarded as despicable or worthless.
- To remove the scum from.
- To become covered with scum.