n.
Pronunciation: ' p ī - ˌ än
Function: noun
Etymology: contraction of pi-meson
Date: 1950
: 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
– pi · on · ic \ p ī - ' ä-nik \ adjective