NAPHTHA Meaning of NAPHTHA in English naph ‧ tha ‧ lene /ˈnæfθəliːn/ BrE AmE ( also naph‧tha /ˈnæfθə/) noun [uncountable] a type of oil used for ↑ fuel or for making chemicals Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012