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

• unthatching
• unthaw
• unthawed
• unthawing
• unthaws
• untheological
• unthickened
• unthink
• unthinkabilities
• unthinkability
• unthinkable
• unthinking
• unthinkingly
• unthinkingness
• unthinkingnesses
• unthinks
• unthorough
• unthought
• unthoughtful
• unthoughtfully
• unthoughtfulness
• unthought-of
• unthread
• unthreaded
• unthreading