naphthene Syllabification: (naph·thene)Pronunciation: /ˈnafTHēn, nap-/Definition of naphthene noun Chemistry any of a group of cyclic aliphatic hydrocarbons (e.g., cyclohexane) obtained from petroleum. Derivatives naphthenicPronunciation: /nafˈTHēnik, nap-, -THenik/ adjective naphthene in other Oxford dictionaries Definition of naphthene in the British & World English dictionary