Here’s yet another, quite different, meaning, which I heard used by a researcher at an AI company:
AIs produce output with recurring tics (“it’s not A — it’s B”, “genuinely”, etc.) that people notice and that start to grate on them
Or perhaps more abstractly:
AIs produce output that many people learn to tell at a glance is from AI
I don’t like that meaning because it’s not really about quality at all, or at most it’s about one narrow aspect of the output’s quality. But it seemed clear that those verbal tics are what the person had in mind when they explained they were working on a new “anti-slop” initiative. And it certainly fits that that’s an aspect which an AI company might want to prioritize.
Personally, when I say “slop” I normally mean something that overlaps with some of the meanings you list but is a bit distinct:
An AI produced something low-quality, and a human chose to post that without bothering to bring it up to reasonable quality.
So it’s about the human’s behavior as much as the AI’s performance. Partly that’s because the contexts where I use the term tend to be something to the effect of “don’t post slop here, it’s a waste of our time and yours”. (And because I know the term is ambiguous, I include a few words defining what I mean by it.)
Rich Dad Poor Dad was a book, whose author worked for years to build it up into a brand. That’s very different from a Google doc, which is what Zach was contrasting with.