unheard-of

In those days, indoor plumbing was almost unheard-of. [=very few people had indoor plumbing]在那个年代，室内管道几乎没人听说过。

He was hired for an unheard-of salary of more than a million dollars.他得到一份一百多万美元薪水的工作，这样的薪水是前所未闻的。

It's not unheard-of for a patient's condition to improve this quickly.患者的病情好得这么快，这在以前不是没有发生过。