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

    Synonym: impregnableinviolablesecurestrongunassailable