quark

(physics) hypothetical truly fundamental particle in mesons and baryons; there are supposed to be six flavors of quarks (and their antiquarks), which come in pairs; each has an electric charge of +2/3 or -1/3; "quarks have not been observed directly but theoretical predictions based on their existence have been confirmed experimentally"

Source: WordNet® 3.1, Princeton University — "WordNet Copyright 2011 by Princeton University. All rights reserved." Used under WordNet's license terms. See methodology for full licensing detail. Word validity for game play may differ from any official game dictionary.