궁구해요 · 궁구했어요 · 궁구할 거예요 · 궁구하세요
to study thoroughly, to investigate deeply
Example
그는 평생 인간의 본성을 궁구했습니다.
He spent his whole life deeply studying human nature.
Word parts
궁 exhaust+구 investigate
Literally 'exhaust and investigate' — studying until nothing is left.