When talk or writing is discursive, it moves from one idea or fact to another, and then another, without always heading toward one clear point. It can feel like a walk with no map: you see many things, but you may not know why you are being taken this way. Teachers and reviewers use it when an essay or a talk covers a lot of ground but will not stay on one path. Though actually, it is not always a scolding. Among friends, thinking aloud is normal; the talk finds its shape as it goes. In a school essay or a work report, the same habit can tire the reader, because those kinds of writing are supposed to have a purpose you can name. Everyday English is more likely to say someone is rambling, going off topic, or jumping around; discursive is the more formal, bookish twin. One more twist: in philosophy the same word can mean almost the opposite — thinking that moves step by step through reasons, not in a sudden flash. In comments on student writing, it almost always means the piece wanders.