uropygial gland[yo͝orˌə-pīˈjē-əl, -pĭjˈē-]
uropygial gland 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.
a large gland located at the base of the tail in most birds, that secretes an oil used in preening
uropygial gland definition by American Heritage Dictionary
A large gland at the base of a bird's tail that secretes an oil used in preening. Also called oil gland.