Here are some synonyms for "ramble on":
* Waffle
* Meander
* Dwell
* Prate
* Blabber
Example:
* "I tried to explain my project to him, but he just rambled on about his weekend."
* "The professor's lecture rambled on for hours, leaving many students confused."
Note: The phrase can be used in both a negative and a neutral way. In some contexts, it can simply mean that someone is talking for a long time, without necessarily implying that they are being boring or repetitive. However, it is more often used in a negative sense to suggest that the speaker is being long-winded or irrelevant.