any of a genus (Listeria, esp. L. monocytogenes) of small, Gram-positive, rod-shaped bacteria that cause listeriosis, sometimes found in dairy products and raw meat
See listeria in American Heritage Dictionary 4
(lĭ-stîrˈē-ə)
noun
Any of various rod-shaped, gram-positive bacteria of the genus Listeria, which includes the causative agent of listeriosis.