Definition of melanism in US English:

melanism

noun

Zoology
  • Unusual darkening of body tissues caused by excessive production of melanin, especially as a form of color variation in animals.

    • ‘Albinism does occur in some populations, but there are no published records of melanism (black fur) in lions.’
    • ‘The work of Burtt and colleagues provides a nice complement to recent work on the genetic basis of melanism in birds.’
    • ‘That pattern of morphological convergence includes larger bills, reduced rust coloration in plumage, and increased melanism or dark coloration.’
    • ‘However, melanism and amelanism are known to occur in many species of natricine snakes.’
    • ‘Adaptations to short, cool summers include activity at low temperatures, selection of warm habitats and microhabitats, melanism and hairiness coupled with basking behaviour, and prolonged or abbreviated life cycles.’

Pronunciation

melanism

/ˈmɛləˌnɪzəm//ˈmeləˌnizəm/