Particle Physics a type of quark with a mass of c. 4.7 to 5.3 GeV/c, a negative charge that is the charge of an electron, zero charm, and zero strangeness
See bottom quark in American Heritage Dictionary 4
noun Abbr. b
A quark with a charge of - 1/3 and a mass about 10,000 times that of the electron. Also called beauty quark. See Table at subatomic particle.