At this point, I consider "Dark Matter" to be a substitute for "Shit We Don't Know About". We know, roughly, how gravity and all these forces are supposed to be

At this point, I consider "Dark Matter" to be a substitute for "Shit We Don't Know About". We know, roughly, how gravity and all these forces are supposed to behave. Certain celestial bodies don't follow those rules according to what we know about both the rules and those bodies. So there's something we don't know about there. Either the body or the rule is missing something. If it's the body, then there's a whole mess of matter that's just imperceptible to our current methods. It is "dark" to our observation.