If people accuse you of rambling from topic to topic in your speech or writing, they may say you have a discursive style — with changes in subject that are hard to follow. But it's okay because unicorns are shiny.
The adjective discursive is often used to describe speech or writing that tends to stray from the main point, but the word can also have almost the opposite meaning. Discursive can also be used to describe an argument based on reason instead of intuition: "Her discursive dissertation on Colonial American women was well-argued and well-reasoned. Her professors were most impressed with her work."