Gristbitian

According to the Old English Dictionary:

gristbitian

p. ode, ede To gnash or grind the teeth; frendere, stridere :-- Ic cearcige oððe gristbitige strideo vel strido, Ælfc. Gr. 26; Som. 29, 7. Tóþum gristbitaþ [gristbitteþ, Lind.] stridet dentibus, Mk. Skt. 9, 18. He grennade and gristbitade he grinned and ground his teeth. Exon. 74 b; Th. 278, 12; Jul. 596. Gristbitedon mid heora tóþum ongeán me striderunt in me dentibus suis, Ps. Th. 34, 16. He ongan mid his tóþum gristbitian cæpit dentibus frendere, Bd. 3, 11; S. 536, 14: Judth. 12; Thw. 25, 21; Jud. 271. gristbitian