unthinkable
adjective uk/ʌnˈθɪŋ.kə.bəl/ us/ʌnˈθɪŋ.kə.bəl/
C1 难以想象的，不可思议的
so shocking that it cannot be imagined as possible
Today, we see growing acceptance of gay marriage - something that would have been unthinkable a generation ago. 今天我们对同性婚姻的接受程度越来越高，在上一代的时候这是难以想象的事。