do what; what to doA colloquial phrase formed from 뭐 (“what”) and 하다 (“to do”). In actual speech, it is normally conjugated, for example 뭐 해? (“What are you doing?”) or 뭐 하는 거야? (“What are you doing?”).
KO: ‘뭐 하다’는 ‘무엇을 하다’의 구어체 표현이에요.
EN: “뭐 하다” is a colloquial expression for “무엇을 하다.”