pocket universe

plural pocket universes

1. A hypothetical realm in inflationary theory, only one of which would contain our observable universe.

   Synonyms: bubble universe

2. gamesA small, self-contained fictional universe that borrows concepts from established universes.

   I set it in a 'pocket universe' based on role-playing games.

   2013, Frank Garcia, Mark Phillips, Science Fiction Television Series, 1990-2004, page 118

   1 more example

   […] the simulationist sought a game system that created "a little pocket universe without fudging."

   2014, Evan Torner, William J. White, Immersive Gameplay, page 79