1
: made of cast iron
2
: resembling cast iron: such as
a
: capable of withstanding great strain
a cast-iron stomach
b
: not admitting change, adaptation, or exception : rigid
a cast-iron will
c
British
: not likely to fail or be broken : airtight
"Clever idea, Black, getting yourself seen on a safe station platform … gave you a cast-iron excuse not to leave your hidey-hole in future, didn't it?"—
J. K. Rowling
J. K. Rowling
: a commercial alloy of iron, carbon, and silicon that is cast in a mold and is hard, brittle, nonmalleable, and incapable of being hammer-welded but more easily fusible than steel
Examples of cast-iron in a Sentence
Adjective
lost weight only after a cast-iron adherence to his diet
he has a cast-iron faith in his innate ability to overcome any adversity that life might throw against him
Noun
The fence is made of cast iron.
Recent Examples on the Web
Karen Brewer Grossman, Southern Living, 30 Dec. 2025
When the radiator is laid on its back, the copper plumbing and heatsinks become visible, showing how heat will be transferred into the cast-iron body.
—Kaif Shaikh, Interesting Engineering, 30 Dec. 2025
Toni Sutton, PEOPLE, 4 Jan. 2026
Follow these easy steps to clean rust off your cast iron.
—Karen Brewer Grossman, Southern Living, 30 Dec. 2025
See All Example Sentences for cast-iron
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Adjective
If your cast-iron pan has rust spots and has seen better days, don’t get rid of it.
—Karen Brewer Grossman, Southern Living, 30 Dec. 2025
When the radiator is laid on its back, the copper plumbing and heatsinks become visible, showing how heat will be transferred into the cast-iron body.
—Kaif Shaikh, Interesting Engineering, 30 Dec. 2025
Noun
Le Creuset Signature 8-Quart Oval Dutch Oven Designed with enameled cast iron, this round 8-quart pot heats quickly and retains heat and flavor efficiently.
—Toni Sutton, PEOPLE, 4 Jan. 2026
Follow these easy steps to clean rust off your cast iron.
—Karen Brewer Grossman, Southern Living, 30 Dec. 2025
See All Example Sentences for cast-iron
Cite this Entry
“Cast-iron.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cast-iron. Accessed 7 Jan. 2026.
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