Marginalized describes a person or a group that has been pushed aside and left with little power or respect. News and school texts talk about “marginalized communities”: people whose voices are easy to skip. It is the same idea as the verb marginalize, but here it is often an adjective sitting in front of a noun. Though actually, it is also just the ordinary past form: they marginalized her / she was marginalized. Careful speakers sometimes prefer “people who have been marginalized,” because the short adjective can start to sound like a type of person, as if being on the edge were a label they carry, not a thing that was done to them. It is a serious, fairly formal word; it is not a playground insult, and it is not a kind nickname.