This is usually used to mean a different civilization or someone outside the dominant group of our own. "Civilized" can be used to refer to the norm-violators in our society, or to people from other "barbaric" (ie, differently normed) societies.
Intra-society, marginalized groups are going to be viewed as less civilized by the dominant group. The the US, this is likely first about class markers. The lower classes, or perhaps the wrong religion, violate the norms of "proper" society. These will also very much correlate with racial divisions, but a black man in America can be viewed as civilized if he acts white -- that is, conforms to the norms of the dominant groups. Also helps if he's wealthy, though a lot of that may stem from classical education correlating with wealth, and bringing about a lot of enculturation in the dominant culture.
Cross-society, "uncivilized" may refer to societies that look similar to where ours was in the past. Oh, you're pastoralist? Some of our ancestors were too, before we settled down. Oh, you're agrarian? Yeah, have you considered concentrating your population in cities like ours?
Our society feels further along the tech and culture tree than those other societies, and that makes them relatively uncivilized. However, in many ways this is just a surface appearance and their society has plenty of complex norms, and it's as accurate for them to describe us as uncivilized for being in violation of those norms.
If a society has well-defined rules, it's civilized, whether those rules are considered barbaric by others. Being civilized isn't about the norms of the upper classes of your particular society. It's about having norms. We live in a society.