Digress (verb)

1. To depart from the main subject or the straight path; to stray from the point.
2. To talk or write about something that is not directly related to the main topic.

Origin:

From latin digredi, meaning "to depart from a subject".

Examples:

1. The speaker digressed from the main topic of his speech.
2. He always digresses when he tells a story.
3. The conversation digressed into a discussion of the weather.
4. She digressed from her original point and started talking about something else.
5. The author digressed from the plot and included a lot of background information.