Also found in: Dictionary, Thesaurus, Medical, Financial, Idioms.
Ink adhering to the nonimage area of a printing plate, resulting in tinting of the nonimage area of the printed substrate.
1. A surface deposit sometimes formed on clay bricks; caused either by soluble salts in the clay which migrate to the surface as moisture escapes during drying (drier scum) or by the formation of deposits during kiln firing (kiln scum).
2. A mass of organic matter which floats on the surface of sewage.