Iron containing carbon in excess of its solubility in the austenite that exists
in the alloy at the eutectic temperature. For the various forms--gray cast
iron, white cast iron, malleable cast iron, and nodular cast iron--the word
"cast" is often left out, resulting in the terms gray iron, white iron,
malleable iron, and nodular iron, respectively.
Source: Dictionary of Mining, Mineral, and Related Terms