This is sort of like asking, 'What do you call something that is neither a rock nor not-a-rock?' If it isn't a rock, then it is automatically not-a-rock - there's nothing in the middle.
I don't think there's term for someone who isn't a theist and isn't an atheist: the two terms together form a universal set.
Put another way, anyone who isn't a theist has to be an atheist, by definition.
Boru
I don't think there's term for someone who isn't a theist and isn't an atheist: the two terms together form a universal set.
Put another way, anyone who isn't a theist has to be an atheist, by definition.
Boru
‘I can’t be having with this.’ - Esmeralda Weatherwax