- impregnable
- adj1. invulnerable, indestructible, undestroyable, imperishable, nonperishable, Obs., Rare. imperdible; invincible, unconquerable, impenetrable, inviolable, inexpugnable; unassailable, unat-tackable, insuperable, insurmountable, undefeatable, unbeatable; formidable, powerful, mighty; tenable, secure, safe, safe and sound; stout, strong, sturdy, solid, stable, staunch, stanch; indomitable, redoubtable, unyielding.2. indisputable, incontestable, irrefutable, undeniable, unquestionable, indubitable, incontrovertible, sure, certain, absolute; unimpeachable, irreproachable; perfect, flawless, unflawed, faultless
A Note on the Style of the synonym finder. 2014.