[verb] [T] - to bring (teeth) forcefully together because of angerIn the film there were green monsters which roared and gnashed their teeth.If you gnash your teeth about something, you complain angrily and noisily about it.Villagers have been gnashing their teeth about the council's decision to build a car park on the meadow.
GNASH
Meaning of GNASH in English
Cambridge English vocab. Кембриджский английский словарь. 2012