The Collaborative International Dictionary
Melanism \Mel"a*nism\ (m[e^]l"[.a]*n[i^]z'm), n. [Gr. me`las, -anos, black.]
An undue development of dark-colored pigment in the skin or its appendages; -- the opposite of albinism.
(Med.) A disease; black jaundice. See Mel[ae]na.
Melanism \Mel"a*nism\ (m[e^]l"[.a]*n[i^]z'm), n. (Ethnol.) The character of having a high degree of pigmentation, as shown in dark skin, eyes, and hair.
Douglas Harper's Etymology Dictionary
Wiktionary
n. congenital excess of melanin pigmentation in the skin, hair, feathers and/or eyes.
WordNet
n. a condition characterized by abnormal deposits of melanin (especially in the skin) [syn: melanosis]
Wikipedia
Melanism is a development of the dark-colored pigment melanin in the skin or its appendages and is the opposite of albinism. Historically, it was also the medical term for black jaundice.
The word melanism is derived from the ("black pigment").
Pseudo-melanism, also called abundism, is another variant of pigmentation, characterized by dark spots or enlarged stripes, which cover a large part of the body of the animal, making it appear melanistic. A deficiency in or total absence of melanin pigments is called amelanism.
The morbid deposition of black matter, often of a malignant character causing pigmented tumors, is called melanosis. For a description of melanin-related disorders, see melanin, melanosis coli and ocular melanosis.
Usage examples of "melanism".
A classic example is the development of industrial melanism in British moths: darker moth individuals became relatively commoner than paler individuals as the environment became dirtier during the 19th century, because dark moths resting on a dark, dirty tree were more likely than contrasting pale moths to escape the attention of predators.