맥이 빠져요 · 맥이 빠졌어요 · 맥 빠지는 + noun
to feel deflated; to lose heart; to be drained
Example
열심히 준비한 행사가 취소돼서 맥이 빠졌어요.
The event we worked so hard on got canceled, and I felt totally deflated.
Word parts
맥 pulse
Literally 'one's pulse drains away' — energy suddenly gone.
Good to know
맥 빠지는 소리 = a remark that takes the wind out of your sails.