melanosisPronunciation: /ˌmɛləˈnəʊsɪs/Definition of melanosis noun [mass noun] Medicine a condition of excessive production of melanin in the skin or other tissue. Derivatives melanoticPronunciation: /-ˈnɒtɪk/ adjective Origin: early 19th century: modern Latin, from Greek melas, melan- 'black' + -osismelanosis in other Oxford dictionaries Definition of melanosis in the US English dictionary