龇牙

bù huì yǎo rén qiè mò zī yá liě zuǐ

不会咬人，切莫龇牙咧嘴。

If you cannot bite never show your teeth.

tā zuǒ tuǐ yī zhèn jù tòng téng de tā zhí zī yá

他左腿一阵剧痛疼得他直龇牙。

He winced as a sharp pain shot through his left leg.