impregnable

• In this difficulty, Kalergy determined to attack the impregnable island-fortress of Grabusa, as it was known that the strength of the place had induced the Turks to leave it with a very small garrison. —  Blackwood's Edinburgh Magazine - Volume 55, No. 344, June, 1844
• This wretch tried every artifice to win her to the desired prostitution; but found all her efforts were vain; for her chastity was impregnable, and she well knew that virtue alone could procure true happiness. —  Fox's Book of Martyrs Or A History of the Lives, Sufferings, and Triumphant Deaths of the Primitive Protestant Martyrs
• When they found our house impregnable, the musicians began to waylay us in the streets. —  My Reminiscences
• Artmouth found it well-nigh impregnable, and Artmouth's backs were reckoned good men If we had three more men in our line as heavy and steady as Browning, Cowan, and Carey," said Devoe, "we might hope to get our backs through; but, as it is, they'll get the jump on us, I fear, and tear up our offense before it gets agoing The only course," answered one of the coaches, "is to get to work and put starch into the line as well as we can, and to perfect the backs at kicking and running. —  Behind the line A story of college life and football
• Their frontier would seem to be impregnable, and the difficulties of invading England, even from the air, are very much as they were during the last war. —  The Great Prince Shan

Roget's II: The New Thesaurus

Used in the Same Context