alternate universe

Noun

alternative universe (plural alternative universes)

1. A hypothetical world situated in a different dimension of space and time than the real world consisting of the universe known and experienced by human beings.
   • In particular, it has been argued that if any of six (or perhaps a few more) numbers did not have rather particular values, then life as we know it would not be possible; atoms would not exist, or no grativationally bound structures would form in the Universe, or some other calamity would occur...2007 June 21, Bernard Carr, editor, Universe Or Multiverse?, page 367

   Synonyms:

   alternative world, heterocosm, parallel world

2. An imaginary realm, often a variant form of the real world or of the fictional universe usually depicted in a work, depicting a different way events could have unfolded or the universe could have functioned.
   • This mirroring was marked out by the way in which the Federation of Planets, a voluntary association of different worlds, never existed in the alternative universe; instead we find ourselves confronting a vicious militaristic Terran empire.2022 June 13, S. Sayyid, Recalling the Caliphate – Decolonization and World Order

   Synonyms:

   alternative dimension, parallel dimension, parallel universe