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• cast iron
  cast iron

  noun

  an alloy of iron, carbon, and other elements, cast as a soft and strong, or as a hard and brittle, iron, depending on the mixture and methods of molding.
• cast-iron
  cast-iron

  adjective

  made of cast iron.

cast iron

¹ American  

noun

1. an alloy of iron, carbon, and other elements, cast as a soft and strong, or as a hard and brittle, iron, depending on the mixture and methods of molding.

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cast-iron ² American  

[kast-ahy-ern, kahst-] / ˈkæstˈaɪ ərn, ˈkɑst- /

adjective

1. made of cast iron.

2. not subject to change or exception.

   a cast-iron rule.

3. hardy.

   a cast-iron stomach.

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cast iron British  

noun

1. iron containing so much carbon (1.7 to 4.5 per cent) that it cannot be wrought and must be cast into shape

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adjective

1. made of cast iron

2. rigid, strong, or unyielding

   a cast-iron decision

Etymology

Origin of cast iron¹

1655–65; cast (past participle of cast ( def. ) ) + iron

Origin of cast-iron²

First recorded in 1655–65

Example Sentences

See Examples For:

cast iron cast-iron

It is also the world's oldest five-arch cast iron bridge.

From BBC ● Jun. 20, 2026

The local authority said the bridge would be kept under close review, and may also close again if further deterioration of its cast iron girders is identified.

From BBC ● Jun. 20, 2026

Laura Cherkas gives Aurora Sanchez a cast iron pan.

From Los Angeles Times ● Apr. 22, 2026

I’ve come to think of cast iron as the fastest way to build depth on a weeknight.

From Salon ● Apr. 21, 2026

I went in and found Rufus in bed with his leg sandwiched between the two boards of a wooden splint and held straight by a device of rope and cast iron.

From "Kindred" by Octavia Butler

This one embraces two of the South’s most cherished cornbread traditions: a well-seasoned cast-iron skillet and bacon drippings.

From Salon ● Jun. 22, 2026

Bryant said the deal would give "cast-iron protections to our key industries to speed up economic growth as part of our Plan for Change".

From BBC ● Dec. 15, 2025

Still, on Black Friday she splurged on items she deemed functional and great temporary deals, including Staub cast-iron cookware and McGee & Co. home decor she has long wanted.

From The Wall Street Journal ● Dec. 5, 2025

Plaza Park has been home to a water feature since March 1887, when a prominent women’s group raised funds to place a three-tiered cast-iron fountain at the center of the park.

From Los Angeles Times ● Aug. 26, 2025

Maybe, someday, a cast-iron gate at the end of the driveway.

From "Born a Crime: Stories from a South African Childhood" by Trevor Noah