Pontificate, verb: “to speak or express your opinion about something in a way that shows that you think you are always right” (Merriam Webster’s definition for those learning english)
The more formal definition they offer is:
to speak or express opinions in a pompous or dogmatic way”Merriam Webster
Synonyms include expound, moralize, lecture and preach. This is rather appropriate since the noun form of pontificate is the duration of time for which a pope serves as, well, pope. It originally comes from Latin, specifically from Pontifex, which was the title of a Roman high priest. The word probably meant something along the lines of bridge-maker or path-maker.
Regardless, pontificate used as a verb today has a negative connotation. While it might be appropriate to describe a priest as pontificating, it’s not something to say if you have a favorable opinion of the sermon.
Pontificate is a nice, all around good word for describing anyone that talks as if from a position of authority. With a synonym of expound, it also tends to imply being long winded.
Anyone with the need to preach or moralize, at length, about a topic, can be said to be pontificate. Heard anyone pontificating lately?