If you say that something is unthinkable, you are emphasizing that it cannot possibly be accepted or imagined as a possibility.
Her strong Catholic beliefs made abortion unthinkable.
笃信天主教使她无法接受堕胎。
The unthinkable is something that is unthinkable.
Teresa Zapata told her family the unthinkable; she was going to work in the United States.
特雷莎·扎帕塔告诉了家人一件他们很难想象的事情,就是她打算到美国工作。