Noun
countershading (usually uncountable, plural countershadings)
A pattern of animal colouration, existing as a form of camouflage, characterised by darker pigmentation of the upper side and lighter of the underside.
Cott built on Thayer's discoveries, developing a comprehensive view of camouflage based on "maximum disruptive contrast", countershading and hundreds of examples. Source: Internet
The term countershading has a second meaning unrelated to "Thayer's Law". Source: Internet
Self-shadowing makes an animal appear darker below than on top, grading from light to dark; countershading 'paints in' tones which are darkest on top, lightest below, making the countershaded animal nearly invisible against a suitable background. Source: Internet
The result is a 'flat' appearance, instead of the 'solid' appearance of the body before countershading. Source: Internet