Uncouthness is the quality of behaving or speaking in a rough, rude way that other people think is not acceptable in polite company. It is the noun for being 'uncouth'. Note what kind of rudeness this is: an uncouth person is not usually trying to hurt anyone. They eat with their mouth open, they talk too loudly in a quiet restaurant, they say the thing everyone was thinking but nobody says, they wipe their hands on their trousers. The problem is a lack of polish, not a lack of kindness. So 'uncouthness' often carries a second flavour that students miss — it says something about the speaker too. When you call someone's behaviour uncouthness, you are placing yourself above them, as a person who knows the rules judging a person who does not. Because of that, the word can sound snobbish, and writers often use it that way on purpose, to show that the person complaining is a snob. It is a formal, bookish word. You will meet it in novels, reviews and opinion writing, and almost never in conversation — in speech people say 'he has no manners' or 'that was so rude'. It usually describes a general quality ('his uncouthness'), but you can also talk about 'the uncouthness of the remark', meaning that one particular thing was crude.

粗俗、沒教養、舉止粗魯（指不懂禮儀、上不了檯面，而非惡意傷人；說人「粗俗」時往往也顯得說話者自視甚高）