衔嚼子

Traditional (Taiwan): 銜嚼子

xiánjiáozi ㄒㄧㄢˊ ㄐㄧㄠˊ ˙ㄗ

    • to keep silent
    • to hold one's tongue

Character by character

Saying俗语俗語

Idiom惯用语 · Rarely used now

Literally
hold the bit in the mouth
Meaning
Said of someone who stays silent, like a horse with a bit in its mouth. Used as a jibe.

Sources