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Meaning of muonium

mu•o•ni•um

Pronunciation: (my-ō'nē-um), [key]
— n. Physics.
  1. an electron and a positively charged muon bound together by electrical attraction in the same manner as the electron and proton in a hydrogen atom.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.