What the hell is that?
How to say "What the hell is that?"? Gracias
¿Qúe diablos es eso? What the hell is that?
Since "infierno" is "hell", would it be ¿Qué el infierno es eso?" I don't know....
I looked this on google a few weeks back and I came up with : ¿Que demonios es eso? The translator seems to agree, but I should tell you that I am not positive about this. You might want to wait for other members to weigh in. I hope this helps.