The angry driver was such a gnasher that you could hear his teeth grinding from the next seat.

### 解释 gnasher 是动词 gnash（咬牙切齿）加后缀 -er 构成的名词，指"经常咬牙切齿的人"。后缀 -er 表示"做某动作的人或物"。 gnash 本身指"牙齿紧咬摩擦"，常用于形容愤怒或痛苦时的表情动作。