Dictionary
Words, grammatical forms and meanings linked to the ontology.
mirror universe en · NOUN
Meanings
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An alternative universe within a fictional work, separate from the universe normally depicted, where familiar characters and settings are present but in a systematically "reversed" manner, often by being evil or otherwise hostile.
Star Trek: The Original Series introduced a mirror universe in which humans had aggressively conquered parts of the galaxy rather than forming the peaceful Federation, and the setting was revisited in several of the franchise's spinoff shows.
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(rare) A hypothetical universe, a counterpart to this universe but with certain elementary particles reversed in a specific way.
A mirror universe of fermions and forces isomorphic to but distinct from those we see couples directly to our universe only by gravity. […] Consequent effects are contrary to experiment. The possible existence of such a mirror universe is thereby excluded.
1986 January 30, S.L. Glashow, “Positronium versus the mirror universe”, in Physics Letters B, volume 167, number 1, page 35:
Forms