nut case nut case {n. phr.} A very silly, crazy, or foolish person. I am going to be a nut case if I don't go on a vacation pretty soon. Categories: add yours crazy {n. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: N Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss