fluxion /ˈflʌkʃən/noun 3verb 1forms 3 noun3 •(no longer used) The derivative of a function. •(no longer used, rare) The action of flowing.Perhaps he meant that towns are after all excrescences, grey fluxions, where men, hurrying to find one another, have lost themselves. — 1907 •(no longer used, rare) A difference or variation. verb1 •To be distributed in a flowing pattern. formsfluxioned · fluxioning · fluxions