to throw shaming words at someone, daring or despising them: to taunt, mock, or defy
This is the meaning the word carries almost everywhere it appears. At its core it is verbal aggression: sharp, cutting words flung at a person, a people, or God in order to shame, belittle, or dare them. The same root noun is the everyday word for an insult, so the verb is the act of hurling one.
The word covers a wide arc of hostile speech, from a soldier's open challenge to single combat, to the jeering of enemies who pile on when someone is already down, to outright contempt for God himself. What holds these together is the posture behind the words: the speaker sets himself above his target and treats that target as beneath respect. When the target is God, the insult becomes defiance of heaven, and a recurring pattern follows: a taunt aimed at Israel or its king is read as a taunt aimed at the God who stands behind them, and God answers it directly. That is why the same word runs through both the Goliath story and Sennacherib's threat against Jerusalem, and why both end with God acting to defend his own honor.
Two edges of the word are worth singling out. In the sayings of the wise, to wrong the helpless poor is described as insulting their Maker, because mistreatment of a person is treated as contempt aimed past them at the God who made them. And in one war song the word stretches to mean holding one's own life cheap, counting it as nothing in the face of death.
Nuances
Whether Judges 5:18 (Zebulun and its life "to death") uses the reproach sense of the word ("scorned, held life cheap") or a separate root meaning "be early, be eager" ("was eager to risk its life").
- majorityThe reproach sense: Zebulun scorned or despised its own life, counting it as nothing in the face of death.; E. Kutsch, חרף, Theological Dictionary of the Old Testament (TDOT), vol. 5
- minorityA separate root meaning "to be early, to be eager" (compared with the Akkadian verb hurrupu): Zebulun eagerly threw its life toward death.; H. Tawil, An Akkadian Lexical Companion for Biblical Hebrew (2009), 120