mad as a hatter . mad as a hatter or mad as a March hare {adj. phr.} Not able to think right; crazy. Anyone who thinks the moon is made of green cheese is mad as a hatter. Categories: add yours crazy {adj. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 » In RussianTo section: M Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss