I often have to explain to my clients about rolling outages. See, this comes into play when you’re doing maintenance, mainly reindexing.
On SQL Standard you can’t reindex online, which means you’ll have table locks that are going to block your users. So here’s how this works… Table1 begins its reindexing and the table is blocked. Nobody can access the table at all. The app complains and so do the users. You even start getting complaints that the DB may be down. Then the reindexing finishes for that table and the locks are released and the users can get back in.
Then Table2 starts its reindexing, and the same thing happens. So Table1 was effectively offline, then Table2, then Table3, etc.
You’ve got a rolling outage. Get it?
This is what I call it. I’ve never heard anyone else use it, but when I say it to DBAs they have no problem working out what I mean. It’s a good term.

This is in fact one of the questions I ask when determining whether we should be on std or ent. Because it’s not a normal downtime as the entire DB isn’t offline. Often times the business can sustain a rolling outage at the right time of day. But it really depends on how large the tables and indexes are. Some tables will have outages of a few seconds, while others can take an hour or longer.