Patsy had to clench her jaw to suppress her anger.

帕茜不得不咬紧牙关来压下怒火。

《柯林斯英汉双解大词典》

The jaw is able to clench and chew because of the masseter muscle.

正是因为有咬肌的存在我们的下巴才能够进行咬合和咀嚼。

youdao

Or just clench your jaw and hang on with white knuckles in terrified silence.

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Her hands may clench before her jaw does.

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