Noun
A hypothetical realm in inflationary theory, only one of which would contain our observable universe.
Synonym: bubble universe
(gaming) A small, self-contained fictional universe that borrows concepts from established universes.
Source: en.wiktionary.orgWe should not act like we know that the universe began with the Big Bang... we'll see that there are strong suggestions that the Big Bang was perhaps not really the beginning of existence, but really just the beginning of our local universe, often called a pocket universe. Alan Guth