It simply means.

WHAT THE F*CK ARE YOU ON?

Say it to someone who says something completely f*cked up...

Or someone on drugs, and you really want to know, what the hell they are smoking.
GUY#1: I think I just saw a purple elephant drinking my beer in the kitchen...

Guy#2: Dude, wtfruo?
by claudzxrawr January 20, 2010
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