cast-iron

1 of 2

adjective

ˈkast-ˈī(-ə)rn 

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

cast iron

2 of 2

noun

: 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

Synonyms of cast-iron

Adjective

• strict
• rigorous
• rigid

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

Adjective

Seasoning your cast-iron grates will prevent rust and discoloration. — Daley Quinn, Southern Living, 12 July 2026

The last was paired with lamb that had been roasted in a cast-iron pot with smoldering herbs and hay. — Adam Erace, Travel + Leisure, 2 July 2026

Noun

Olewack warns that older plumbing materials, such as cast iron, may be corroded and leaking, and that most homeowners choose to replace these older materials with PVC. — Kamron Sanders, The Spruce, 18 July 2026

The lightweight carbon steel body heats water quickly while remaining easier to lift than cast iron alternatives, and the durable porcelain enamel resists rust and scratches. — Better Homes & Gardens, 16 July 2026

Word History

First Known Use

Adjective

1692, in the meaning defined at sense 1

Noun

1664, in the meaning defined above

Rhymes for cast-iron

• aileron
• antiphon
• autobahn
• carillon
• castellan
• celadon
• cephalon
• cynodon
• denouement
• deuteron
• echelon
• epsilon

Kids Definition

cast iron

noun

: a hard brittle alloy of iron, carbon, and silicon shaped by being poured into a mold while melted