underfur definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
the softer, finer fur under the outer coat of some animals, as beavers and seals
underfur definition by American Heritage Dictionary
The soft, fine undercoat of certain mammals, such as otters, beavers, and seals.