impregnable /im-pregˈnə-bl/

1. That cannot be captured, broken into or taken by force
2. Which cannot be overcome, unassailable

impregnabilˈity noun

impregˈnably adverb

• ultramicroscopic
• ultramicroscopy
• ultramicrotome
• ultramicrotomes
• ultramicrotomy
• ultramontane
• ultramontanes
• ultramontanism
• travelling rug
• travelling rugs
• travellings
• travelling-wave tube
• travelling-wave tubes
• travelog
• travelogs
• travelogue
• travelogues
• travels
• travel-sick
• travel sickness
• travel-soiled
• travel-stained
• travel-tainted
• traversable
• traversal