DIVAGATE

digress, stray, divagate, wander

(verb) lose clarity or turn aside especially from the main subject of attention or course of argument in writing, thinking, or speaking; “She always digresses when telling a story”; “her mind wanders”; “Don’t digress when you give a lecture”

Source: WordNet® 3.1

Etymology

Verb

divagate (third-person singular simple present divagates, present participle divagating, simple past and past participle divagated)

(intransitive) To wander about.

(intransitive) To stray from a subject or theme.

Source: Wiktionary