As I posted elsewhere, it's a meaningless, undefined term, and as such it just shouldn't be used. Officially, it's "expensive to make", maybe technically something like "in the top 3% of games based on development cost (including marketing?)". But it's been used so much by gamers to talk about...just not being an indie, I guess, that it's even been robbed of that meaning.
Technical discussion (heck any meaningful discussion) should ditch the term and look at what one thinks 'AAA' means within their argument. So if you are going to use 'AAA' to mean expensive, say 'expensive', and if you would use 'AAA' to mean high quality, use 'high quality'. Otherwise people are arguing at cross-purposes over their own interpretation of 'AAA'.
Edit: I think in terms of how it's typically used to differentiate bigger games from others, they could maybe be called 'major' titles and 'minor' or 'secondary'. A publisher's major titles are the more expensive projects being predicted to make good returns for the investment. Their minor titles are extras, more risky, smaller in scope, that may or may not break out. UE5 is a great facilitator of such minor titles.
Primary and Secondary (and even tertiary), or Major and Minor (and 'tentpole' for major franchises)?
