放冷炮

fànglěngpào ㄈㄤˋ ㄌㄥˇ ㄆㄠˋ

    • to do something unexpected that catches others off guard

Character by character

Saying俗语俗語

Idiom惯用语 · Rarely used now

Literally
fire a cold cannon
Meaning
To do something unexpected that catches others off guard.

Sources