impregnable
1 Americanadjective
-
strong enough to resist or withstand attack; not to be taken by force, unconquerable.
an impregnable fort.
- Synonyms:
- invulnerable
- Antonyms:
- vulnerable
-
not to be overcome or overthrown.
an impregnable argument.
- Synonyms:
- unassailable
adjective
adjective
-
unable to be broken into or taken by force
an impregnable castle
-
unable to be shaken or overcome
impregnable self-confidence
-
incapable of being refuted
an impregnable argument
adjective
Synonym Usage
See invincible.
Other Word Forms
Derived Forms
Etymology
Origin of impregnable1
First recorded in 1400–50; late Middle English impregnable, imprenable, from Middle French, equivalent to im- im- 2 + prenable pregnable
Origin of impregnable2
Explanation
When something is impregnable it is not easily taken by force and can stand up to any attack. We usually use it in reference to some form of protection, like a fort or a solid defensive line in football. The genealogy of the adjective impregnable includes the Middle French word prenable, meaning "vulnerable, easily conquered," which itself came from the verb prendre, which meant "to take." The addition of the negative prefix im- flipped the meaning. Impregnable can be used to describe anything that cannot be entered or successfully attacked. Seventeenth-century theater critic Jeremy Collier once said, "True courage is a result of reasoning. A brave mind is always impregnable."
Vocabulary lists containing impregnable
Power Suffix: -able
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1984
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"Joyas Voladoras" by Brian Doyle
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Though the Cuban government has acknowledged talks, Díaz-Canel warned last month that “any act of aggression will clash with an impregnable resistance.”
From The Wall Street Journal • Apr. 3, 2026
In 2015, the seemingly impregnable Central Belt – and beyond – in Scotland fell to the Scottish National Party from Labour.
From BBC • Dec. 30, 2025
Singapore was considered impregnable, but it wasn’t prepared for an attack from the mainland, and its 60,000-strong garrison surrendered on Feb. 8, 1942, the worst defeat in British history.
From The Wall Street Journal • Oct. 27, 2025
“It’s like hitting a bullet with a bullet,” someone says, crushing the naive notion of an impregnable “nuclear defense.”
From Los Angeles Times • Oct. 9, 2025
The great clipper, so seemingly impregnable, had become impossibly small.
From "Ship Breaker" by Paolo Bacigalupi
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
