efflux n. + Add to list US //ˈɛfɫəks// ef·flux Archaic SynonymsAntonymsEtymology Synonyms effluenceoutflow Antonyms inflowinfluxOriginLATeffluxus→ENefflux From Latin effluxus, from effluō (“flow out or away”), from ex (“out of, from”) + fluō (“flow”). See also effluxion.