sententious

If you speak in sententious phrases, your listeners are probably falling asleep, as your speech is pompous and pretentious, and full of moralistic babble.

When sententious first appeared in English — back in the late Middle Ages — it meant "full of wisdom," but now it usually has a negative sense, meaning heavy handed and self-important. The sententious blowhard makes people laugh, and you can probably think of at least three cartoon characters who fit the bill — often a politician or minister who drones on and on, oblivious to the fact that his audience is snickering or trying to sneak out.