The scene of the car accident was so hideous that I couldn't sleep for days.

hideous 是形容词，由词根 hide（隐藏）和后缀 -ous（充满...的）组成，字面意思是"令人想躲藏的"。引申为"极其丑陋的、可怕的"，形容令人极度不适或恐惧的事物。