The fly agaric mushroom.
fly agaric definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a poisonous mushroom (Amanita muscaria) usually having an orange or russet cap with white flakes and white gills
also fly amanita
Origin: origin, originally used as a fly poison
fly agaric definition by American Heritage Dictionary
A poisonous mushroom (Amanita muscaria) usually having a red or orange cap with white gills and patches.