epilithicPronunciation: /ˌɛpɪˈlɪθɪk/Definition of epilithic adjective Botany (of a plant) growing on the surface of rock: most seaweeds are epilithicOrigin: early 20th century: from epi- 'upon' + Greek lithos 'stone' + -icepilithic in other Oxford dictionaries Definition of epilithic in the US English dictionary