1. 耐侵蚀的：unassorted 未分级的;未分选的 | unattackable 耐侵蚀的 | unattenuated 未变稀的;未变细的
adj
1. immune to attack
incapable of being tampered with
e.g. an impregnable fortress
fortifications that made the frontier inviolable
a secure telephone connection