If it's a 3-tier scale, the middle "doing your job" means you use your 8 hours / day to get work done (mostly). You don't push off as many duties as possible while "waiting" for more information. You don't go fishing while logging hours. You continue to see what you can get done throughout the day, and you do it, even if you're not being watched and monitored.
On that bottom tier, unless something is specifically measurable, unless there's a solid grasp of accountability that management can use to ensure the work you're doing is meaningfully productive from their point of view, you don't have to do much of anything. You could be in sales but not selling anything. You could show up for required meetings, but make up reasons why you didn't get anything done. You could spend 7 of your 8 hours watching Netflix. Basically, you quietly (as in, without being noticed) quit (as in, stopped doing your job.)
So many people do this already while spending all their time disrupting others and working long hours.
That is an interesting phrase. Isn't this what is required of you to do? If you are failing at the job, you will at least get noticed.
So, what is quiet quitting? In my mind, it seems like not having ambition to grow in the corporate world is (negatively) called out as quiet quitting.