divagate
/dɪˈvæɡeɪt/Definitions
1. verb
to wander or stray from the subject; to digress; to talk idly or inconsequently
“The professor’s lecture began to divagate, covering a wide range of unrelated topics.”
2. noun
a wandering or straying from the subject
“The student’s divagation made it difficult for the others to follow the discussion.”