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<blockquote>a type of light we could perceive as black because our eyes ... do not</blockquote>

That's anything in the EM spectrum other than visible light.  So exclude roughly 400 to 750 nm wavelengths.  Infrared and ultraviolet are obvious choices, being on either side of the visible spectrum.

<blockquote>eyes and brain ... do not understand it</blockquote>

It's not about the brain, and therefore "understanding".  The limitation is the spectral sensitivity of the sensors in your retina, and also the filtering effect of the optical pathway (the sensors can detect some UV, but it is filtered by the eye before it gets to the sensors).

If you're looking for something you can "shine" somewhere to create a dark spot, that's not how the physics works<sup>1</sup>.

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<sup>1</sup> It is possible for one coherent light beam to appear to cancel another in a localized area, but that doesn't seem to be at all what you're after, and ambient light isn't going to be coherent in any kind of "normal" circumstance anyway.