any of a genus (Amanita) of mushrooms (order Agaricales), with white spores and, usually, white gills, some of which, as the death cap and the fly agaric, are very poisonous
See amanita in American Heritage Dictionary 4
(ămˌə-nīˈtə, -nēˈ-)
noun
Any of various mushrooms in the genus Amanita, many of which are extremely poisonous.