Having black pigmentation, especially in the context of genetics. A melanic is, like an albino, rare in the wild, because they are easily seen: most individuals have some form of cryptic coloration.
Examples of melanism are the black panther, which is a form of leopard; and the peppered moth Biston betularia, which famously showed the effect known as industrial melanism, increasing in frequency as the Industrial Revolution covered parts of Britain in soot near factories and towns, and receding once the Clean Air Acts had allowed lichens on trees to be seen again.