If you describe something as unimaginable, you are emphasizing that it is difficult to imagine or understand properly, because it is not part of people's normal experience.
例句
The scale of the fighting is almost unimaginable...战斗的规模几乎无法想象。The children here have lived through unimaginable horrors.这里的孩子经历了难以想象的恐惧。
英汉词典释义
adj.
不能想象的；难以想象的；想不到的
Such speed of travel was unimaginable before the railway age.这样的车速在铁路时代之前是不可想像的。We all believed it unimaginable that he had lived alone on a deserted island for so long.我们都觉得他在渺无人迹的荒岛上住这么久是不可想象的。