고사해요 · 고사했어요 · 고사할 거예요 · 고사하세요
to decline firmly, to turn down politely
Example
그는 장관직 제의를 끝내 고사했어요.
He ultimately declined the offer of a minister's post.
Word parts
고 firm+사 decline
Literally 'firmly decline': refusing an honor or offer, usually out of modesty.
Good to know
Homonyms: 고사하다 can also mean 'to wither' (枯死); -는 고사하고 means 'let alone.'