Synonyms: inviolable, impregnable, unassailable, unattackable, strong, secure
Definition: immune to attack; incapable of being tampered with
Usage: an impregnable fortress; fortifications that made the frontier inviolable; a secure telephone connection
Similar words: invulnerable
Definition: immune to attack; impregnable
Usage: gunners raked the beach from invulnerable positions on the cliffs