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parallel universe

American  
[par-uh-lel yoo-nuh-vurs] / ˈpær əˌlɛl ˈyu nəˌvɜrs /

noun

  1. Physics. any of a hypothetical collection of undetectable universes that are like our known universe but have branched off from our universe due to a quantum-level event.

  2. (in cosmology) a hypothetical universe that coexists with our known universe but may operate under fundamentally different laws of physics.

  3. Also called alternate universe,.  Also called alternative universe.  (in science fiction, fantasy, etc.) a separate universe or world that coexists with our known universe but is very different from it.

  4. a realm of existence and experience that is fundamentally different from the one that most humans share; a separate reality.

    I don’t understand him—I think he lives in a parallel universe.

Etymology

Origin of parallel universe

First recorded in 1920–25

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.