/kwawrk, kwahrk/ , n.
Physics. any of the hypothetical particles with spin 1/2, baryon number 1/3, and electric charge 1/3 or -2/3 that, together with their antiparticles, are believed to constitute all the elementary particles classed as baryons and mesons; they are distinguished by their flavors, designated as up (u), down (d), strange (s), charm (c), bottom or beauty (b), and top or truth (t), and their colors, red, green, and blue. Cf. color (def. 18), flavor (def. 5), quantum chromodynamics, quark model .
[ coined in 1963 by U.S. physicist Murray Gell-Mann (b. 1929), who associated it with a word in Joyce's Finnegans Wake, read variously as E quark croak and G Quark curd, (slang) rubbish, tripe ]