a. [ See Uropygium. ] (Anat.) Of or pertaining to the uropygium, or prominence at the base of the tail feathers, in birds. [ 1913 Webster ]

Uropygial gland, a peculiar sebaceous gland at the base of the tail feathers in most birds. It secretes an oily fluid which is spread over the feathers by preening. [ 1913 Webster ]

‖n. [ NL., fr. Gr. &unr_;, (corrupted form) &unr_;; &unr_; the end of the os sacrum + &unr_; rump. ] (Anat.) The prominence at the posterior extremity of a bird's body, which supports the feathers of the tail; the rump; -- sometimes called pope's nose. [ 1913 Webster ]