UCF: Acronym for the United Cat Federation.

Ulcer: A lesion of the skin or a mucous membrane such as the one lining the stomach or duodenum that is accompanied by formation of pus and necrosis of surrounding tissue, usually resulting from inflammation or ischemia.

Unaltered: Term referring to a male or female cat who has not been neutered or spayed and has full reproductive abilities.

Undercoat: The layer of the coat comprised of down hairs.

Undercolor: A term referring to the color of the hair closest to the skin.

Uterus: A hollow muscular organ located in the pelvic cavity of female mammals in which the fertilized egg implants and develops. Also called womb.