꾸벅꾸벅 졸다 (ggu-beok-ggu-beok jol-da) – doze off
꾸벅꾸벅 means “drowsily” and 졸다 means “to doze off”.
But “dozing off drowsily” doesn’t make much sense in English so just understand the phrase as an exaggeration of “doze off”.
운전하면서 꾸벅꾸벅 졸지 말고 우리 생명은 너 나름이야.
Don’t doze off while driving, our lives depend on you.
그 남자가 똑똑하지만 수업 시간 자꾸 꾸벅꾸벅 졸아서 좀 아까워.
That guy is smart but he always doze off during class so it’s a pity.