gnash

例句：

1. 1. The dog gnashed its teeth in frustration.
   狗因沮丧而咬着牙。
2. 2. She gnashes her teeth while she talks.
   她说话时咬着牙。
3. 3. The child gnashes his gums as he fidgets.
   孩子因为不安而咬着牙。