primarily, "to bit or eat greedily" (akin to bruko, "to chew"), denotes "to grind or gnash with the teeth," Act 7:54.
primarily used of the sounds of animals, "to chirp, cry, squeak," came to signify "to grind or gnash with the teeth," Mar 9:18. akin to A, No. 1, denotes "gnashing" ("of teeth" being added), Mat 8:12, Mat 1:13,50, Mat 22:13, Mat 24:51, Mat 25:30, Luk 13:28.