Describes a person who is emotionally healthy — who copes with problems, gets on with other people, and is generally comfortable in their own life. It is used most often about children and teenagers ('a well-adjusted child'), and about someone who has come through something hard and turned out fine: 'considering everything he went through, he's remarkably well-adjusted.' It carries a slightly clinical flavour, because it comes from psychology, so it sounds a little more distant and measured than saying someone is 'happy' or 'a good kid'. That distance is useful — it lets you talk about mental health without prying. There is also a mild irony in how adults use it: praising a young person as well-adjusted can sound like praising them for fitting in, and some speakers use it that way on purpose, half-joking, half-critical. The opposite is 'maladjusted', which sounds heavy and old-fashioned now; people are more likely to say someone is 'struggling'. Keep the hyphen when the word sits before a noun ('a well-adjusted student'); after the verb, writers often drop it ('she seems well adjusted'), and both are accepted.