To look down on someone means to think you're better than they are, to feel superior and treat them as less important or capable. When someone looks down on others, they might dismiss their ideas in a meeting, make snide comments about their clothes or interests, or act like spending time with them would be beneath them.

This attitude shows up everywhere: a student might look down on classmates who struggle with math, forgetting that those same kids might excel at art or music. A wealthy person might look down on someone with less money, missing the fact that wealth doesn't measure character or intelligence.

When used this way, it's entirely about attitude, about treating someone as inferior. The opposite would be looking up to someone, which means respecting and admiring them.