leptomeninges Syllabification: (lep·to·me·nin·ges)Pronunciation: /ˌleptōməˈninˌjēz/Definition of leptomeninges noun Anatomy the inner two meninges, the arachnoid and the pia mater, between which circulates the cerebrospinal fluid. Derivatives leptomeningealPronunciation: /-ˌmenənˈjēəl/ adjective leptomeninges in other Oxford dictionaries Definition of leptomeninges in the British & World English dictionary