Wiktionary
phr. (non-gloss definition: An intensive form of '''what'''.)
Usage examples of "what the deuce".
Wondering what the deuce this was about, I broke the seal - and had a sudden premonition of what I would read.
Besides, he will very likely wonder what the deuce it has to do with me, and I'm sure I can't tell him!
If you want to know what I think, old man, your pal UnderhillI can't imagine what the deuce you see in him, but, school together and so forth, makes a difference, I suppose,I say, if you want to know what I think, Freddie, the blighter Underhill would be well advised either to leg it after Jill and get her to marry him or else lie low for a goodish while till people have forgotten the thing.
I could hear my own knees creaking as I crouched there, scratching the newly-healed bullet-wound in my backside and wondering what the deuce was wrong.
But at least I could answer - though what the deuce it could mean to this foppish monster was far beyond me.