'Smooth' in the Bible

For no faith may be put in their words; their inner part is nothing but evil; their throat is like an open place for the dead; smooth are the words of their tongues.

Everyone says false words to his neighbour: their tongues are smooth in their talk, and their hearts are full of deceit.

The smooth lips and the tongue of pride will be cut off by the Lord.

You make the ploughed lands full of water; you make smooth the slopes: you make the earth soft with showers, sending your blessing on its growth.