a hard, unmalleable alloy of iron made by casting: it contains a high proportion of carbon and silicon, has low tensile strength, and is very fluid and fusible when molten
adjective
made of cast iron
very hard, rigid, strong, healthy, etc.
See cast iron in American Heritage Dictionary 4
noun
A hard, brittle, nonmalleable iron-carbon alloy, cast into shape, containing 2 to 4.5 percent carbon, 0.5 to 3 percent silicon, and lesser amounts of sulfur, manganese, and phosphorus.
adjective
Made of cast iron.
Rigid; inflexible: a cast-iron rule.
Exceptionally strong or resistant: a cast-iron stomach.