digress
1. [ verb ] lose clarity or turn aside esp. from the main subject of attention or course of argument in writing, thinking, or speaking
Synonyms: divagate wander stray
Examples:

"She always digresses when telling a story" "her mind wanders" "Don't digress when you give a lecture"

Related terms: tell diversion digression
2. [ verb ] wander from a direct or straight course
Synonyms: straggle stray depart sidetrack
Related terms: deviate straggle
Similar spelling:   digressive
  digression
  disgorge
  disrespect
  disgrace
  degressive