| unattackable 
 
 immune to attack;
 incapable of being tampered with
 - an impregnable fortress
 - fortifications that made the frontier inviolable
 - a secure telephone connection
 • Syn:
 impregnable, inviolable, secure, strong, unassailable
 • Similar to:
 invulnerable
 • Derivationally related forms:
 impregnability (for: impregnable), secureness (for: secure)
 
 
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