1. a former name for the muon, an unstable subatomic particle with a mass between that of an electron and a proton
Usage: physics; historical

Examples

• The mesotron was discovered in cosmic ray experiments in the 1930s.
• Scientists later renamed the mesotron to muon to avoid confusion.
• The mesotron has a very short lifespan before it decays.
• Early particle physicists studied the properties of the mesotron extensively.
• The term mesotron is now considered obsolete in modern physics.