I am going to describe them as they are commonly used, not how a dictionary might define them if you look at all 6 or 7 definitions :) Crass and rude are only used to describe a person's action and speech. "Crass" means not very polite and too direct. Usually it is insulting, but not always. It is not a nice thing to be called. If someone calls you "crass," it is not a compliment :) "Rude" is when you are saying things that are insulting. Coarse and rough are very close to each other. Coarse is more educated, formal, and specific. It is less commonly used. It only refers to things that are not smooth or pleasing to touch. Rough can be used in many other ways, so it is a weaker word. Both can be used to describe behavior or speech, but it is different from crass or rude because rude is always insulting and crass is usually insulting. A person could be coarse or "rough" just because of how they were raised or where they live. People who are farmers or live very far from a city might generally be considered "coarse" or "rough." "Unrefined" is similar: a person who is not very cultured, not very educated. If you call someone unrefined, it usually sounds a little.... condescending. You are saying you are superior to them. You are refined, whereas they are not. But sometimes, if your tone of voice is right, it can sound like a gentler way to say the other words you have asked about. "Crude" is usually a lot like crass but it tends to be used when the words are more sexual, like saying disrespectful things about women or talking about sex in a coarse way :)

you might add 'uncouth'

I suggest that you consult: www.thefreedictionary.com

Thank you very much, Leaf. That is very helpful!