to press your top and bottom teeth together, often in anger

He gritted his teeth in silent fury. 他气得咬牙切齿，一言不发。

to accept a difficult situation and deal with it in a determined way

We had to grit our teeth and agree with their conditions because we wanted the contract. 因为我们想要拿到那份合同，就必须咬牙答应他们的条件。