The Latin word inexpugnabĭlis arrived in Spanish as impregnable . This term has three meanings recognized by the Royal Spanish Academy (RAE ) in your dictionary.
The resulting place impossible to conquer or to dominate Through the use of weapons receives the qualification of impregnable. For example: "The terrorist group has an impregnable stronghold in the north of the country", "Because of its geographical location, the island was always impregnable: no foreigner could conquer it throughout history", "The army leaders believed that the city was impregnable, but it took ten days for the invader to overcome its resistance".
He site or enclosure to which it results very difficult to access It is also mentioned as impregnable: “Nature itself made, with the growth of vegetation, the pre-Hispanic citadel to be impregnable”, "This prison is impregnable: nobody can arrive or leave without being seen by the sentries", "It is believed that tons of land cover the remains of the impregnable palace".
Other use of impregnable is associated with what cannot be overcome, reversed or defeated : "The defense of the local team was impregnable: despite the efforts of the rival, the goal was never at risk", "After the reports of harassment, the actor maintained an impregnable public silence for more than a year", "It is important that users accept that no antivirus is impregnable".
As you can see in the various examples , impregnable can be used physically or symbolically. A structure buried by thousands of kilograms of land is impregnable since no person can reach it; a silence that does not break by the will of the individual is, in a metaphorical sense, impregnable.