Contrast between 'things', on the edge of 'things', separation of colours, often helped in understanding by having used Contax G lenses. Sharpness is sharper than contrast although lenses can provide both. I don't think you are pedantic, you just look for ways to trip people up, it's nice to have hobby's. But if you are baffled Google something like 'lens micro contrast' and you'll find even the Ai bot understands it.
My question was/is sincere and I feel it's not really answered if the answer involves "you'll have to use this lens in order to get it". Arguments relying on (quasi-)technical parameters are too often of a self-immunizing, tautological nature, which doesn't help at all. And yes, I'm baffled, as you would be if you would think a little harder about what you just wrote down, which in the end really doesn't say much at all.
If we strip the tautological bits off, what remains is something like:
"Contrast between things on the edge of things" as micro-contrast - which seems to come close to how resolving power is measured. I also don't want to conflate resolving power and sharpness, but the fact that these constructs are so close to each other does emphasize the need to disentangle them.
In an attempt to make things a little more concrete, I'm thinking along these lines:
Contrast is the difference in value (intensity, luminosity, density) between any two given points.
Micro contrast is the contrast between points in close proximity; this still leaves considerable leeway in what we would consider 'close'. Maybe in the context of 35mm film, it would be something on the sub-mm scale; perhaps something in the order of magnitude of 10um. By nature of that definition, it would essentially be the definition of resolving power, which, after all, is the ability of an optical system to distinguish between different values of luminosity/density/illumination in close proximity.
Macro contrast would be equivalent, but at a larger physical scale - across the entire frame or significant parts of it.
We could apply contrast to monochrome or color - ultimately it's luminosity or density in any given channel/wavelength.
Sharpness is a much more tricky concept since it seems to be a subjective impression that results from a combination of several things. This will include micro-contrast (as it determines resolving power), but also a set of more or less unrelated factors like granularity (or noise), non-linear modifications to the transfer function (e.g. the 'ringing' nature of unsharp masking), etc. I'm not sure if we'll ever get any further than establishing that it's subjective and complex, and that ultimately it involves but is not limited to aspects like resolving power.
If you move even further away from the realm of measurable, tangible parameters, we end up in the area where constructs like 'color pop' live, which ultimately have no definition that can sensibly linked to the performance of an optical system, at least without defining them in terms of observable parameters and operationalizing them. We may then have a fighting chance at making claims at whether a certain lens might offer more of it than any other.
What I see happening here, as in many places, is that we never really get to that point. My remark was a challenge open to all to see how far we might get on that route. And I made it in the full awareness that there's probably a limit to how far we can take it and before things just get very subjective and perhaps even personal. That's OK, but I feel it's still more useful to give it a try than to stick with the photographic end-all of the "you gotta see it in order to believe it."
PS: AI doesn't 'get' anything. That's why it's not useful to engage it in this case, since conceptual thinking is simply not part of its feature set.
