a lepton similar in most respects to the electron except that it is unstable, it may be positively charged, and its mass is approximately 207 times greater; the positively charged muon is the antiparticle of the negatively charged muon. Symbol: μ
An elementary particle in the lepton family having a mass 209 times that of the electron, a negative electric charge, and a mean lifetime of 2.2 X 10-6 seconds. The muon was originally called the mu-meson and was once thought to be a meson. See Table at subatomic particle.