"down to earth" means realistic, practical, earth-grounded

To me, a down-to-earth person is someone who acts naturally. For example, he does NOT eat a sandwich with a fork. For example, when he speaks, he does NOT use "big" words to impress people. For example, she does NOT wear expensive clothes because all the other women are doing so. Therefore, if you tell somebody that she is the LEAST down-to-earth person that you have ever met, then you are saying that she is the most UNnatural- acting person whom you have ever met.

It's a little insulting to say this of someone because "down-to-earth" also includes the qualities of being humble and approachable, not just practical.

I like down-to-earth people. They are usually sensible, practical, capable, approachable, and often give good solid advice. I am down-to-earth in some ways, but not in others! I am not always very sensible. Also, I make a lot of fuss about some things - minor things that I really should ignore. So, again, that is not a very down-to-earth approach.

Eric: Conceptually, there exists the basic reality of a common understanding. This refers to common awareness, common understanding, common knowledge, common premises and common assumptions. Everybody employs common assumptions or a "common ground" even if they do not articulate it explicitly. Any person who uses discriminating thought can discover unstated assumptions even if another person does not explicitly state the hidden assumptions. There can be common ground as to Social Customs, Cultural Understandings and practices and Basical knowledge as is known to exist in Science, Philosophy, Theology, Law, and the Arts and History. If a person lacks an awareness of these common assumptions, suppositions and presuppositions, their communication with other people will appear awkward, disjointed, confused or unclear.