To speak tediously and at great length (about something). He just kept rattling on about literary metaphors and imagery. I didn't know what he was talking about!I caught myself starting to fall asleep while the professor rattled on.
rattle on (about someone or something)
Fig. to talk endlessly about someone or something. Martin talked incessantly. He would rattle on about any topic whenever he could trap an unfortunate listener.
rattle on
v.
To talk continuously about something, especially to others not as interested in the subject as the speaker is: They kept rattling on about how much fun they had at the party, but I didn't really care.