to curse: to pronounce a solemn, binding curse of harm against a person
This is a strong word for cursing. It does not mean casual swearing or foul language; it names the deliberate act of speaking a curse out loud so that harm will fall on its target. The curse is treated as effective, a spoken doom that does real damage once it is uttered.
More than half its appearances come from one story: the prophet Balaam, hired by King Balak of Moab to curse Israel (Numbers 22 to 24). Balak keeps demanding a curse, and Balaam keeps discovering he cannot deliver one, because a curse spoken against people God has blessed has no power. The tension of that whole account turns on this verb, repeated again and again as Balak insists and Balaam refuses.
Outside that story the word carries the same weight in everyday life. Proverbs warns that people will curse the man who hoards grain in a famine, and that whole nations will curse the judge who calls the guilty innocent. Job pictures skilled cursers ready to lay a curse on a day itself. In every case the curse is a public, spoken pronouncement meant to bring ruin, the mirror opposite of a blessing.
Hebrew has several words in this family, and they overlap: אָרַר is the broad, common word for putting someone under a curse, קָלַל leans toward treating a person as contemptible, זָעַם is the angry denunciation, and נָקַב is a near-twin so close that scholars debate whether it is the same root. Against them, this verb is the formal, potent pronouncement of doom.