Rangy describes a body with long, thin, strong legs — a person, a horse, a dog — not much spare flesh, but a look of strength. It is not merely thin. Thin can mean weak or small; rangy suggests length you could use, as if the body was made to cover ground. Sports writers like it for tall players who take long strides. You will hear it more in American English than in a young learner’s textbook. It can feel admiring, or at least physical and exact, rather than unkind. From range plus a describing ending: the kind of build that can range over a wide space. Though actually, it does not mean “good at a wide range of things”; that is a different use of range.

四肢修長而結實