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.)
which no sooner comes on him, but it throws him down: then the child foams, gnashes his teeth, and grows meager.
When they heard these things, they were transported with rage, and gnashed their teeth against him.