quark /kwɑːk, kwɔːk $ kwɔːrk, kwɑːrk/ BrE AmE noun [countable]
[ Date: 1900-2000 ; Origin: Invented by Murray Gell-Mann (born 1929), U.S. scientist, based on the phrase "three quarks for Muster Mark" in Finnegans Wake (1939) by James Joyce; because originally there were thought to be three quarks ]
technical a very small part of something, which is smaller than an atom