impregnable

adjective
1
an impregnable building is so strongly built that it cannot be entered by force
غیرقابل تسخیر, نفوذناپذیر
2
strong and impossible to defeat or change
تسخیرناپذیر, شکست‌ناپذیر
The team built up an impregnable 5–1 lead.
the seemingly impregnable Nazi regime
synonym invincible