kāi kǒu chéng zāng
(Internet slang) to use foul language (pun on 出口成章[chu1 kou3 cheng2 zhang1])
开
kāi
to open (transitive or intransitive)
口
kǒu
mouth
成
chéng
short name for Chengdu 成都[Cheng2 du1]
脏
zāng
dirty
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