挂牌子

Traditional (Taiwan): 掛牌子

guàpáizi ㄍㄨㄚˋ ㄆㄞˊ ˙ㄗ

    • to make one's identity openly known
    • to act under a borrowed name

Character by character

Saying俗语俗語

Idiom惯用语 · Rarely used now

Literally
hang up a signboard
Meaning
To make one's role or identity openly known, or to act under a borrowed name or pretext. The sense depends on context and can be neutral or critical.

Sources