to mock with proud contempt; a scoffer who sneers at correction
This is the word behind the scoffer of Proverbs, the most hopeless figure in the book of wisdom. He is not the naive young person who simply has not learned yet, nor the dull person who learns slowly. The scoffer is the one whose problem is his attitude, not his ability: he treats correction as beneath him, sneers at the people trying to teach him, and turns every rebuke into something to ridicule. Proverbs warns that you cannot fix him by reasoning with him, only contain the damage he does to others.
The action behind the noun is a kind of speech that twists what is plain into mockery. Where one person speaks to carry the truth across to another, the scoffer bends his words into derision instead. That is why the same Hebrew root that produces an honest go-between (see the second meaning) also produces its opposite: the scoffer is a spokesman gone wrong, using the gift of speech in reverse.
In Proverbs the scoffer belongs to the home and the classroom, the youth who refuses his teacher. In the prophets the word turns public and political: it names the arrogant leaders of Jerusalem and the plotters at a drunken king's table. One of its sharpest lines is a reversal: God scoffs at the scoffers, answering proud contempt with contempt in kind.