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 anger has torn and hated me; He gnashes on me with His teeth; my enemy sharpens his eyes at me;
The wicked shall see and be vexed; he shall gnash with his teeth and melt away; the desire of the wicked shall perish.
All your enemies have opened their mouth against you; they hiss and gnash the teeth; they say, We have swallowed her up. Certainly this is the day that we looked for; we have found, we have seen.
And wherever he seizes him, he dashes him. And he foams and gnashes his teeth and pines away. And I spoke to Your disciples that they should cast him out, and they could not.
And hearing these things, they were cut to their hearts. And they gnashed on him with their teeth.