1 capitalized : a genus of free-living amebas (family Acanthamoebidae of the order Amoebida) found especially in soil and freshwater either in the form of feeding and asexually replicating trophozoites or dormant double-walled cysts and including several (as A. culbertsoni and A. castellanii) which are pathogenic in humans causing infections of the skin, respiratory tract, eye (as keratitis especially in contact lens wearers), and brain (as meningoencephalitis especially in immunocompromised individuals).