ichthyosis Syllabification: (ich·thy·o·sis)Pronunciation: /ˌikTHēˈōsis/Definition of ichthyosis noun Medicine a congenital skin condition that causes the epidermis to become dry and rough like fish scales. Derivatives ichthyoticPronunciation: /-ˈätik/ adjective ichthyosis in other Oxford dictionaries Definition of ichthyosis in the British & World English dictionary