Yeah, right after I sold, I tried the not being busy thing. It was less than ideal and it only took a few years before I was bored beyond belief. I did the volunteering thing but that was, for many reasons, less than ideal. So, now I keep myself occupied in unofficial capacities, both at home and in my small community.
I'm not sure how people do it. They retire and seem to do a whole lot of nothing. They may travel a little, maybe putter in the garden, but they mostly seem to watch television and hang out with other old people.
I retired fairly young. That may account for some of the difference. I try to have hobbies that keep me both physically and mentally occupied. Being unoccupied doesn't work well for me.
I think "retired" is OK. A lot (most?) retired people who are healthy do something whether it's just some DIY around the house or volunteering. Of course, these days there are opportunities to pick up some dollars through various gig economy things though I would definitely have to need the money.
The lines are more blurred than they used to be though. I've known quite a few consultants who basically wound things down over time--not actively pursuing work as much but happy to spend some time and cash some checks with existing clients.