形容词

1. 匪夷所思的；不可思议的；难以想象的
If you say that something is unthinkable, you are emphasizing that it cannot possibly be accepted or imagined as a possibility.

2. 匪夷所思的；难以想象的；不堪设想的
You can use unthinkable to describe a situation, event, or action which is extremely unpleasant to imagine or remember.

1. incapable of being conceived or considered