산통을 깨요 · 산통을 깼어요 · 산통 깨지 마
to ruin everything; to spoil a plan
Example
깜짝 파티였는데 동생이 말해 버려서 산통을 깼어요.
It was a surprise party, but my brother blurted it out and ruined everything.
Word parts
산 calculate+통 tube
산통 was a fortune teller's tube of sticks; breaking it ruins the reading.
Good to know
Not 산통 'labor pains'.