unthinkable /ˌʌnˈθɪŋkəbəl/ adjective Learner's definition of UNTHINKABLE
[more unthinkable; most unthinkable]
: impossible to imagine or believe不能想象的;不可相信的 : too bad or shocking to be thought of不可思议的;难以想象的
the unthinkable
: something that you cannot accept, believe, or imagine
especially : something that is so bad that you do not want to think about it难以接受之事;不可思议之事;(尤指)不可想象的极其不好的事情