Cast Iron

Part of speech: noun (n.)

Highly carbonized iron, the direct product of the blast furnace; -- used for making castings, and for conversion into wrought iron and steel. It can not be welded or forged, is brittle, and sometimes very hard. Besides carbon, it contains sulphur, phosphorus, silica, etc.

Part of speech: adjective (a.)

Made of cast iron. Hence, Fig.: like cast iron; hardy; unyielding.