to overwhelm with sudden terror: to fall upon a person with dread that seizes from outside
This is the Hebrew Bible's word for being ambushed by terror. It does not name a fear that grows in someone or a steady dread they carry; it names the shattering moment when dread falls on a person from the outside, all at once. The classic pictures are violent: an evil spirit seizing King Saul, floodwaters engulfing a drowning man, an angel's drawn sword freezing David in place, God's own arrows finding their mark.
The word has two faces, and they are two sides of the same event. One is the outside force doing the seizing, so that a spirit, a flood, or God himself falls upon and overwhelms the victim. The other is the victim's own collapse, struck helpless and unable to move or think. It sits among several neighboring words for fear, and the contrast sharpens what it means: פחד is the dread that builds up beforehand, the thing you brace for; חתת is the aftermath, the broken nerve once terror has done its work; חרד is the visible trembling of the body. This word names the strike itself, the instant of being fallen upon.
Half of all its appearances sit inside the book of Job, where it becomes Job's own term for a God he feels has turned aggressor: "you terrify me with visions," "let his dread not overwhelm me." The single most memorable use, though, is in Esther, where the schemer Haman, who had terrorized a whole people, is himself struck with this sudden terror the moment he realizes his plot has collapsed. The fear does not creep up on him. It arrives whole.