허무주의가 · 허무주의를
nihilism
Example
그는 전쟁을 겪은 후 깊은 허무주의에 빠졌어요.
After going through the war, he fell into deep nihilism.
Word parts
허 empty+무 nothing+주 main+의 doctrine
Literally 'empty-and-nothing-ism'.
Good to know
The everyday adjective is 허무하다: 인생이 허무해요 (Life feels empty).