Green’s Dictionary of Slang

1. careless, blasé.

1986

J. Ellroy Silent Terror 73: [D]evouring the food with the what-the-fuck panache of men determined to die young.

2. uncomprehending.

2006		G. Malkani Londonstani (2007) 128: The guys all looked at each other with their funniest what-the-fuck faces.
2007		W. Ellis Crooked Little Vein 52: I made a whatthefuck face at Trix.