1.
one's natural hair; real hair
A person's own natural hair, as opposed to dyed hair, a wig, or extensions. Refers to both the natural color and texture of one's hair.
Usage
地毛 is commonly used in conversations about hairstyling and school dress codes. In Japan, some schools require students with naturally light-colored hair to submit a "地毛証明書" (natural hair certificate) to prove their hair is not dyed.
The 地 in 地毛 means "natural" or "base," as in one's original, unaltered state. This is the same 地 found in words like 地声 (natural voice) and 地肌 (bare skin).