unthinkable

adj. /ʌnˈθɪŋ.kə.bəl/ C1

难以想象的

So shocking or unlikely that it cannot be imagined.

仙境例句

For the Pigeon, sleeping even one hour was unthinkable while serpents were near.

对鸽子来说，蛇就在附近，连睡一个钟头都是想都不敢想的事。