Exact Match:
- impregnable
- incapable of being overcome, challenged or refuted; "an impregnable argument"; "impregnable self-confidence"
- able to withstand attack; "an impregnable fortress"; "fortifications that made the frontier inviolable"
Synonyms:
- deathless,
- defended,
- guarded,
- immortal,
- impenetrable,
- imperishable,
- incontestable,
- incorruptible,
- indelible,
- indestructible,
- indomitable,
- ineffaceable,
- ineradicable,
- inexpugnable,
- inextinguishable,
- insuperable,
- invincible,
- inviolable,
- invulnerable,
- irresistible,
- mighty,
- nonperishable,
- overpowering,
- overwhelming,
- protected,
- quenchless,
- resistless,
- safe,
- safeguarded,
- secure,
- shielded,
- unassailable,
- unbeatable,
- unconquerable,
- undampable,
- undefeatable,
- undestroyable,
- undying,
- unquenchable,
- unsubduable,
- unsurmountable,
- unyielding