Definition of "muon" [muon]

• An elementary particle in the lepton family (not a meson), having a mass 209 times that of the electron, a negative electric charge, and a mean lifetime of 2.2 × 10-6 seconds. Also called mu meson. See Table at subatomic particle. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "It was then realized that the particle found by Anderson could not be the meson of strong interactions, since it interacted far too little with matter, and it was then shown that this particle, now called the muon, is a heavy cousin of the electron."
• "A muon from a neutrino interaction in the AMANDA neutrino telescope at the South Pole."
• "The muon is about 207 times heavier (106 MeV/c2) and belongs to the second family."