cyanosis: a bluish discoloration of the skin and mucous membranes; a sign that oxygen in the blood is dangerously diminished (as in carbon monoxide poisoning)
symptom: (medicine) any sensation or change in bodily function that is experienced by a patient and is associated with a particular disease
hafnium: a grey tetravalent metallic element that resembles zirconium chemically and is found in zirconium minerals; used in filaments for its ready emission of electrons