1ADJ-GRADED (人)虚情假意的,虚与委蛇的 If you describe someone as unctuous, you are critical of them because they seem to be full of praise, kindness, or interest, but are obviously insincere. (人)虚情假意的,虚与委蛇的 [formal, disapproval]
...the kind of unctuous tone that I've heard often at diplomatic parties.