• (n.) The state or quality of being imaginary; unreality.
Im·ag'i·na·ri·ness noun The state or quality of being imaginary; unreality. 
imaginary, imaginarily, imaginariness 1. Existing only in the imagination. 2. Lacking factual reality; such as, imaginary fears or imaginary illness. 3. Relating to or containing imaginary numbers, or being the coefficient of the imaginary part in a complex number.