expression, pronoun
who the heck; just who (is that)?
Emphatic version of 誰, used when the speaker is suspicious, annoyed, or wants to stress that the person's identity is unknown or questionable. Often rhetorical.
どこの誰だか知らないけど、勝手に入らないで。
I don't know who the heck you are, but don't come in without permission.
あんなことを言うのは、一体どこの誰なんだ？
Who on earth would say something like that?