unbreakable
英 [ʌnˈbreɪkəbl] 美 [ʌnˈbreɪkəbl]
adj.
无法打破的;牢不可破的
相关例句：
Chicago has always been a place where Europeans and North Americans have come together. And now, we have come together to reaffirm the unbreakable bond between us.
芝加哥一直是欧洲和北美紧密联系在一起的地方。而现在，我们一起来重申和美国之间牢不可破的关系。
One unbreakable rule in our school is that no child can be tested without written parental permission.
我们学校有一条金科玉律：未经父母书面同意，不得对学生进行测试。
