Definition of pion
: a meson that is a combination of up and down quarks and antiquarks, that may be positive, negative, or neutral, and that has a mass about 270 times that of the electron
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Recent Examples of pion from the Web
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The most famous of these two-quark particles are kaons and pions.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'pion'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Origin and Etymology of pion
contraction of pi-meson
First Known Use: 1950
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