What does “sajaseongeo” mean in Korean?

A 사자성어 is an idiom exactly four syllables long, each syllable a Sino-Korean character, learned and used whole: 일석이조 (one stone, two birds), 사면초가 (surrounded by enemy songs, meaning hopelessly cornered). Koreans meet them at school and hear them in speeches and headlines, so four syllables can carry an entire argument on their own.

The fixed length is what makes them jokeable. In the clip a teacher asks for the 사자성어 that describes drunken shouting in the street, and the class fires back 고음불가 (“can’t hit the high notes”), 미친 건가 (“has he lost it?”) and 이럴 수가 (“no way”) — all four syllables, none of them idioms. The ones with a story behind them get their own label: 고사성어.