arupa - no form
nirguna - no guna
nirakar - no character
If you study the words above, it is negation of a positive state. For example, if I say "no money", it means there is no money. If I say "no water", means there is no water. It is simple right! But in order to negate a positive thing, that thing first of all has to exist. So now let us look at "no money". Does it mean no money as in there is no money currently or there is no such thing as money? It actually means there is no money but to say there is no such thing as money in creation ever is illogical.How can we negate that which never exists?
Similarly, people use the above words to describe Brahman as arupa, nirguna, nirakar etc and then claiming God has no form, quality etc. But if we use the no money simile, then we have to conclude that for negating the positive word "form" (arupa), first of all there has to be form (rupa). So this positive word "form" so far in our experience is tied to our reality which is material. So when we use the word arupa , then we can only say it is negation of material form and not complete negation of that attribute ever.
But certain class of vedic followers make that jump by saying that arupa means no form at all ever hence God is formless ever. But why cannot God have a spiritual form and still be arupa because our experience of rupa is material.
Therefore, more accurate interpretation of the words describing Brahman is the absence of material form, quality and character etc but certainly the positive state of form, character and quality exists in Brahman and because Brahman is all spirit, that positive state is also spiritual.