As @kayawalton said, Adobe defines a bounce as a "Single Hit" in the visit... For my company, we didn't like that definition, as so we created our own "Bounce" based on "Single Page Visits".
Exit Links, even if enabled, will only count when someone clicks on a link on your page that takes you off the site... using the browser's back button, or closing the tab wouldn't trigger any additional server calls (unless you have some custom JS detecting the "page unload").
For the most part, a user who enters the site and doesn't interact with anything would be counted as a bounce in both the Adobe default bounce as well as the custom bounce that I talked about... but if there are any interactions (a scroll tracker, a overlay shown, any other action hit), this is where the two diverge.
I believe GA4 adds some logic to their bounces (i.e. Engaged Time less than a second), but since this requires an additional tracking call, to replicate this in Adobe would almost double your server call usage (and would break the default bounce metric).
So, what does a bounce mean to you and your organization? You can use Adobe's, or you can create your own... the choice is really up to you.
