From Yahya Abdal-Aziz:

Re: Other universes may be detectable, published study claims (Oct. 11): As you so rightly say:

It’s a rath­er dodgy con­cept on its face, be­cause strictly speak­ing, “the un­iverse” means ev­er­ything that ex­ists.But in prac­tice, cos­mol­o­gists of­ten loos­en the def­i­ni­tion and just speak of “a un­iverse” as some sort of self-en­closed whole with its own phys­i­cal laws.

Rather than coining the ugly and illogical “multiverse”, it might have been better had cos­mol­o­gists adopted a new term with the strict meaning ‘a self-en­closed whole with its own phys­i­cal laws’ - or if that seems too vague, ‘a closed convex region of space-time with its own phys­i­cal laws’. The term that immediately springs to mind when discussing a region with its own specific laws is, of course, a “jurisdiction”. Then the “universe” could rightly remain “ev­er­ything that ex­ists”, and comprise some kind of collection of “jurisdictions”.