Black color is simply a color that does not allow any reflection. Without reflection no visibility could happen. A red color, a perfect red color, absorb everything and reflects only and only red color. While a black color, absorbs every ray which hits it. That is the reason behind its shades also. A dark gray color (with 80% black and 20% white) absorbs 80% of the light it receives and only returns 20% of it. While a black color, as you have mentioned, which is a perfect 100% black color, never allows any ray to be reflected off from it.
Now, we have shiny black, which might confuse our answer a little. A shiny black is not a color, but it is a type of material. It is very significant to not miss the point. Assume a sphere which is perfectly black while it also has some reflections. Is it possible? A perfect black to have some reflections? That's it, as I have already mentioned, that is a material. It is a little complicated apparently, but I dare describing it: A color is fully an abstract idea. One of the attributes of matter is color. Then, the constitutive parts of a material which are particle in shape, and express special behavior when contacted by a light ray. They are inherent within the material. Now, a shiny black, like a leather wallet, has two distinct [color-related] materials. A shiny top-coat, and secondary black surface. Shiny material has its own description, but do briefly throw some light upon it, it is a [relatively] noiseless material which does not allow light to distract (diffusion) and allows a focused reflection. It only allows a portion of light to pass throw it (the amount of shininess); and the rest of the rays are reflected from it. Now the amount which pass throw it, reach the black layer. And thus are devoured by black layer. Conclusion: the amount of reflected light from shiny surface is merged (multiplied) by the amount of non-reflected light, and making a black material which has shines over it.
So again we see blackness is the absence of reflected natural rays visible by unequipped human eyes.
A last note: Science is separated from metaphysics, it is science that makes decision and should be the criterion of our talks. Metaphysical philosophers were stupid in science. They were lazy to discover the phenomenon, and if they discovered, they probably failed at dissecting it. However, we have scientist who had metaphysical activity; anyway, when we talk about their discovery, we still refer to them as scientist. :)
(I have not corrected the misspellings; sorry for that)
The above definition that I have proposed, are from my experience in Animation and Visual Effects.