Heb harak, meaning "to grate the teeth", (Job 16:9; Ps 112:10; La 2:16), denotes rage or sorrow. (See also Ac 7:54; Mr 9:18.)
His wrath has torn, and he has been hostile toward me; he gnashed at me with his teeth. My foe sharpens his eyes against me.
[The] wicked sees [it] and is vexed. He gnashes his teeth and {becomes weak}. [The] desire of [the] wicked perishes.
They have opened their mouths against you, all your enemies. They hiss and gnash a tooth, and they say, "We have destroyed [her]! Surely this [is] the day we have hoped for; we have found [it], we have seen [it]!"
And whenever it seizes him, it throws him down and he foams at the mouth and grinds his teeth and becomes paralyzed. And I told your disciples that they should expel it, and they were not able [to do so].
Now [when they] heard these [things], they were infuriated in their hearts and gnashed [their] teeth at him.