unthinkable

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。

The unthinkable had happened – his secret activities had been discovered by the press.

难以想象的事发生了——他的秘密活动被新闻界发现了。