Search Result for "down quark":
Wordnet 3.0

NOUN (1)

1. a stable quark with an electric charge of -1/3 and a mass 607 times that of an electron; 



WordNet (r) 3.0 (2006):

down quark
    n 1: a stable quark with an electric charge of -1/3 and a mass
         607 times that of an electron