The word that means to talk on and on pointlessly, without clear direction is ramble. This word is also used in cases where a person roams or moves about in an aimless fashion. Ramble can also mean stroll or amble about. Tina lost the attention of the class as she started rambling about the subject and her classmates could not make head or tail about what she was talking about. This is a good example for the word rambling for people to understand the usage of the word.