impregnable /im-pregˈnə-bl/

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

impregnabilˈity noun

• centinell
• centinel private
• centipede
• centipedes
• centner
• centners
• cento
• centoist
• centoists
• centonate
• centonel
• centonell
• centones
• centonist
• centonists
• centos
• centr-
• centra
• central
• central angle
• central angles
• central bank
• central banks
• central conic
• central conics