to give a formal often extended talk on a subject <the eminent professor harangued for three hours on his favorite subject, the clash of East and West>
to talk as if giving an important and formal speech <a talk-show guest using the interviewer's questions as an opportunity to harangue on a variety of pet peeves> Related Words rant
Seen & Heard
What made you want to look up harangue[verb]? Please tell us where you read or heard it (including the quote, if possible).