啞口 ê2kao2

One gets to hear ê2giaⁿ2 啞仔 or ê2 啞 or ê2nang5 啞人 for people who are unable to speak. 

However, there is a word ê2kao2 which you will hear in this video and this means to act as dumb or speechless. You will hear him saying zu6kao2 as well. 

ê2kao2 啞口｜哑口

as if dumb, speechless

ya3kou3啞口｜哑口

zu6kao2 住口

Shut up!

bi4zui3 閉嘴｜闭嘴zhu4kou3 住口

Please note. kao2 is not gao2 狗 as in a dog. The kao2 is like ghua7kao2 外口 as in outside.