gnash
/næʃ/verb
with obj.
1- grind (one's teeth) together, typically as a sign of anger咬（牙）（多表示愤怒）：
no doubt he is gnashing his teeth in rage.
毫无疑问他正气得咬牙切齿呢。
1.1
- no obj.(of teeth) strike together; grind（牙齿）互相叩击; 磨牙：
the dog's jaws were primed to gnash.
那狗正准备要磨牙。
词源
late Middle English: perhaps related to Old Norse gnastan 'a gnashing'.