Meaning of countershading

coun•ter•shad•ing

Pronunciation: (koun'tur-shā"ding), [key]
— n. Zool.
  1. the development of dark colors on parts usually exposed to the sun and of light colors on parts usually shaded, esp. as serving for protection or concealment.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.