ironclad

1 of 2

adjective

iron·​clad ˈī(-ə)rn-ˈklad 

1

: sheathed in iron armor

—used especially of naval vessels

2

: so firm or secure as to be unbreakable: such as

a

: binding

an ironclad oath

b

: having no obvious weakness

an ironclad case against the defendant

ironclad

2 of 2

noun

iron·​clad ˈī(-ə)rn-ˌklad 

: an armored naval vessel especially of the mid to late 19th century

Examples of ironclad in a Sentence

Adjective

The company has an ironclad policy against revealing secrets to competitors.

He has an ironclad alibi.

Recent Examples on the Web

Adjective

Jessie Buckley, an ironclad lock, earned Hamnet’s sole trophy in Best Actress, while Guillermo Del Toro’s Frankenstein cleaned up in the craft categories but was a nonfactor anywhere else. —David Sims, The Atlantic, 16 Mar. 2026

This time around — with concerns heightened not only because of a war with Iran, but also a recent shooting at a university in Virginia and an attack on a synagogue in Michigan — security is going to be even more ironclad, authorities said. —Hannah Fry, Los Angeles Times, 13 Mar. 2026

Noun

The ironclad’s tenure at sea was short-lived, however. —Andrew Paul, Popular Science, 11 Mar. 2026

Even so, there are signs that the ironclad hold has begun to fray, at least a bit. —Luis Melecio-Zambrano, Mercury News, 13 Feb. 2026

Word History

First Known Use

Adjective

circa 1847, in the meaning defined at sense 1

Noun

1862, in the meaning defined above

Rhymes for ironclad

• cephalad
• galahad
• libertad
• undergrad
• ad
• add
• bad
• brad
• cad
• clad
• dad
• fad

Kids Definition

ironclad

1 of 2 adjective

iron·​clad -ˈklad 

1

: covered by iron armor

2

: rigorous sense 1, exacting

ironclad laws

ironclad

2 of 2 noun

iron·​clad -ˌklad 

: an armored naval vessel