This is the 18156th most frequent Korean word.
수포
"수포" means "bubble" or "blister."
Here, '수포' refers to 'bubbles' as physical entities.
그는 수포의 문제를 풀려고 노력했다.
He tried to solve the problem of bubbles.
In this case, '수포' is used metaphorically, meaning 'efforts gone to waste'.
공부한 모든 것이 수포로 돌아갔다.
Everything he studied came to naught.
Here, '수포' denotes 'blisters' as a medical condition.