/ˈmeləˌnizəm/
Noun
1. A development of dark-colored pigment in the skin or its appendages and is the opposite of albinism. Historically, it was also the medical term for black jaundice. (wikipedia.org)
2. Congenital excess of melanin pigmentation in the skin, hair, feathers and/or eyes; the condition of being melano. (wiktionary.org)
3. Unusual darkening of body tissues caused by excessive production of melanin, esp. as a form of color variation in animals. (Google Dictionary)
4. A condition characterized by abnormal deposits of melanin (especially in the skin). (wordnetweb.princeton.edu)
5. An increased amount of black or nearly black pigmentation (as of skin, feathers, or hair) of an individual or kind of organism. (merriam-webster.com)
Word origin: From Greek melano-, comb. form of melas (genitive melanos) “black, dark, murky”