爬牆頭

Simplified: 爬墙头

páqiángtóu ㄆㄚˊ ㄑㄧㄤˊ ㄊㄡˊ

    • to cheat by peeking at others' exam papers
    • to sneak off to steal or have affairs

Character by character

Saying俗语俗語

Idiom惯用语 · Widely known

Literally
climb over the wall
Meaning
Originally sneaking off to steal or have illicit affairs; now mostly cheating by peeking at others' exam papers.

Sources