unctuous: Physically, unctuous means oily or greasy. It comes from the same etymological source as unguent, which is an ointment or salve. Metaphorically, unctuous describes a person who uses "oily" smooth speech. The definition in Webster's New World Dictionary (4th Edition) is so well-written that I'll just quote it here: "characterized by a smug, smooth pretense of spiritual feeling, fervor, or earnestness, as in seeking to persuade; too oily in speech or manner."
(I don't often come along a dictionary definition that I actually enjoy reading. They're often dry and formulaic —"of or pertaining to X," "in a Y manner" — and it's easy to forget sometimes that there are real people, lexicographers, with different levels of creativity, eloquence, and flair behind each definition in a dictionary. Perhaps the alliteration in this definition is what brings it out. It is certainly written in such a way that it could be easily read alound unctuously.)
Anyway, back to the word unctuous: The Fonz had unctuous hair. Pimply teenagers have unctuous faces. Televangelists use their unctuous soliloquies as a lubricant to slide money from the wallets of the lonely and uncertain into their own pocketbooks.
It's a great word to remember during Scrabble, if you ever end up with three U's on your tray.