Korean to English translation question

[javiskefka]

What does this word, "대체" mean when used at the beginning of a sentence, as in the following example?

대체 여긴 어떻게 들어왔지? 폐쇄된 곳인데.

And here is another example of this word, used in a line of a song:

지금 어디 있나요 대체 어디서 뭘 하나요

It seems to mean something like "instead" here.

[manyakumi]

대체 is same with 도대체 and it means "in the world","on earth","the heck","the hell", etc.

너는 누구냐? = Who are you?
대체 너는 누구냐? = Who the hell are you?

여긴 어떻게 들어왔지? = how could you come in?
대체 여긴 어떻게 들어왔지? = how on earth could you come in?

[javiskefka]

Thanks. These emphasizing words are hard to understand, so it helps to have a native speaker's interpretation.