from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A semistable meson produced either in a neutral form with a mass 264 times that of an electron and a mean lifetime of 8.4 × 10-17 seconds or in a positively or negatively charged form with a mass 273 times that of an electron and a mean lifetime of 2.6 × 10-8 seconds. Also called pi meson. See Table at subatomic particle.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any of three semistable mesons, having positive, negative or neutral charge, composed of up and down quarks/antiquarks.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a meson involved in holding the nucleus together; produced as the result of high-energy particle collision
Contraction of pi meson.(American Heritage® Dictionary of the English Language, Fourth Edition)
From pi + -on, as alteration of pi-meson. (Wiktionary)