Meaning: Deceitful, seductive.
Isaiah 30:10
Which say to the seers, See not; and to the prophets, Prophesy not unto us right things, speak unto us smooth things, prophesy deceits:
Proverbs 5:3
For the lips of a strange woman drop as an honeycomb, and her mouth is smoother than oil:
Jeremiah 12:6
For even thy brethren, and the house of thy father, even they have dealt treacherously with thee; yea, they have called a multitude after thee: believe them not, though they speak fair words unto thee.