상전벽해가 · 상전벽해를
a complete transformation, drastic change over time
Example
이 동네는 10년 사이에 상전벽해가 되었어요.
This neighborhood has changed beyond recognition in ten years.
Word parts
상 mulberry+전 field+벽 blue-green+해 sea
Literally 'mulberry fields turned into blue sea' — the world changed completely.
Good to know
Pronounced [상전벼캐]; often describes cities or neighborhoods redeveloped beyond recognition.