Words to Describe impregnability

How impregnability often is described ("________ impregnability")

• moral
• essential
• greater
• apparent
• old
• reputed
• natural
• former
• formidable
• relative
• logical
• american
• brazen
• own
• virtual
• comparative
• serene
• stern
• near
• military
• clad
• utter
• complete
• absolute
• very
• fancied