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
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.
In theory that threatens Apple’s impregnable walled garden.
From The Wall Street Journal • Jan. 2, 2026
Once impregnable, touring sides have won more matches at the Gabba than any other Australia venue since 2021.
From BBC • Dec. 1, 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
High-flying Crystal Palace are the only side to rival City's attacking threat, while Newcastle are living up to their name by being almost as impregnable at the back as Arsenal.
From BBC • Oct. 15, 2025
When it was finished it would be impregnable: no giant, no troll, no dwarf, no mortal would be able to breach that wall.
From "Norse Mythology" by Neil Gaiman
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.
