Prion n. Any of several types of protein particle lacking nucleic acid, believed to be the cause of certain slow-developing infectious diseases such as scapie in sheep, and Creutzfeldt-Jakob disease and Kuru in humans. (informal)
... "Besides the prion, there is the 'mutton-bird' of the whalers (AEstrelata lessoni), a large Procellanid, as big as a pigeon, white and brown ... — A Dictionary of Austral English • Edward Morris