Prion

n.

1.

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.

Noun

1.

prion - (microbiology) an infectious protein particle similar to a virus but lacking nucleic acid; thought to be the agent responsible for scrapie and other degenerative diseases of the nervous system

microbiology, particle