underhair
/ˈʌndərˌhɛr/
noun
- The short, soft, fine hair that grows beneath the longer outer hair of an animal, providing insulation.
- When grooming the cat, the brush removed a lot of loose underhair.
- The dog's underhair keeps it warm during the cold winter months.
- Arctic foxes have a dense underhair that protects them from freezing temperatures.