the perverse fool: a person whose settled disposition rejects wisdom, correction, and the fear of God, not someone of low intelligence
This is one of the Bible's harshest words for a fool, and it is a moral word, not an intelligence word. The standard reference works are unusually agreed on this: the problem with this kind of fool is not that he cannot understand, but that he will not be taught. He despises correction, mocks at being put right, and is sure his own way is best. The fool is quarrelsome, quick to show his anger, and cannot hold his tongue. Above all he treats wisdom and discipline with contempt, which is why the book of Proverbs sets him directly against the person who fears the Lord.
The senses below are the same fool seen at two scales. Most of the time, especially in Proverbs and once in Job, the word names an individual moral type, the obstinate person the wise are warned not to waste their breath on. But the prophets pick the word up and aim it higher, at a whole class of supposedly wise advisers, or at the entire covenant people, turning a domestic warning into a national indictment.
What ties it all together is the refusal to be formed. The folly of this fool is treated as something he has chosen and grown into, not something he was born unable to escape. Proverbs even pictures it as so deeply set in the adult that you could grind him like grain in a mortar and not separate him from it. Yet the one Psalm that uses the word leaves a door open: there fools who have brought ruin on themselves by their sins cry out to God and are healed, so the Bible holds the fool's hardness and the possibility of rescue together without fully resolving the tension.