noun.
Any of a group of naturally occurring dark pigments, especially the pigment found in skin, hair, fur, and feathers.
The Century Dictionary and Cyclopedia
noun.
The black pigment of the hair, choroid, retina, and epidermis of colored races; also, the dark pigment seen in melanæmia and in melanosarcoma and melanocarcinoma. The pigments in these cases may, however, be different.
the GNU version of the Collaborative International Dictionary of English
noun.
A black pigment found in the pigment-bearing cells of the skin, in the epithelial cells of the external layer of the retina (then called fuscin), in the outer layer of the choroid, and elsewhere. It is supposed to be derived from the decomposition of hemoglobin.