Impregnable

Antonyms for impregnable:

helpless, conquerable, sterile.

Synonyms for impregnable:

Sense 1

formidable.

Sense 2

indomitable, dangerous, The.

defensible

tenable.

unconquerable

invincible, unconquerable.

Other synonyms and related words:

hard, inviolable, conceptive, dangerous, solid, good, insuperable, safe, stiff, impervious, warm, substantial, unbeatable, dependable, infrangible, tenable, sacrosanct, untouchable, unafraid, formidable, unstoppable, The, insurmountable, invincible, potent, indomitable, impenetrable, firm, untroubled, absolute, unshakable, watertight.

all (adjective)

secure, unassailable, unattackable, inviolable, strong.

impossible (adjective)

insurmountable.

insurmountable (adjective)

unconquerable.

reasonable (adjective)

tenable.

safe (adjective)

secure.

unconquerable (adjective)

inexpugnable.

unyielding (adjective)

invulnerable, solid, firm, strong, invincible, impenetrable, unassailable, secure.

Sense 2 (noun)

indomitable, invincible.

impregnable (noun)

secure, unassailable, inexpugnable, unattackable, invulnerable, inviolable, unconquerable, strong.

Usage examples for impregnable:

• But besides this natural obstacle to invasion, the mouth of the river is defended by a fort, which from its situation may be pronounced impregnable. - "The Campaigns of the British Army at Washington and New Orleans 1814-1815", G. R. Gleig.
• She had expected an impregnable barrier of mock stupidity. - "The Passionate Elopement", Compton Mackenzie.
• It is said that nothing is proof against gold,- that the strongest tower will not be impregnable, if Jupiter makes love in a golden shower. - "The Works of the Right Honourable Edmund Burke, Vol. XII. (of XII.)", Edmund Burke.