impregnable /im-pregˈnə-bl/

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

impregnabilˈity noun

• pubescence
• pubescences
• pubescent
• pubic
• pubio-
• pubis
• pubises
• public
• public act
• public address system
• public address systems
• publican
• publicans
• public art
• publication
• publications
• public attorney
• public attorneys
• public bar
• public bars
• public bill
• public bills
• public companies
• public company
• public convenience