얼굴이 두꺼워요 · 얼굴이 두꺼웠어요 (ㅂ irregular)
to be shameless, to have a lot of nerve
Example
그는 얼굴이 두꺼워서 매일 돈을 빌려 달라고 해요.
He's so shameless that he asks to borrow money every day.
Word parts
Literally 'one's face is thick,' too thick to blush.
Good to know
Unlike English 'thick-skinned,' this means shameless, not emotionally tough.