Hideous means extremely ugly or unpleasant to look at, so much so that it's almost shocking or disturbing. When something is hideous, it's so unattractive that it might make you want to look away or even feel a little disturbed.

A hideous monster in a story might have warty skin, jagged teeth, and misshapen features that make readers shudder. A hideous scar might be raised, discolored, and startling to see. Someone might describe a particularly ugly building as hideous if its design seems harsh, clashing, or deeply unpleasant. The word carries a sense of revulsion, a strong reaction beyond mild dislike.

People also use hideous to describe things that are morally shocking or terrible, like a hideous crime or hideous behavior. In this sense, it means something so wrong or cruel that it seems monstrous.

When you call something hideous, you're saying it's genuinely hard to look at or think about, the kind of thing that provokes a strong negative reaction.