From Longman Dictionary of Contemporary Englishnutcasenut‧case /ˈnʌtkeɪs/ noun [countable] informal CRAZYMENTALLY ILLsomeone who behaves in a crazy way SYN idiot He’s a complete nutcase.
Examples from the Corpus
nutcase• And Philip thought if anyone was a nutcase it was that boy in the wood.• A nutcase, without a doubt.• My personal assistant was my high school sweetheart, Mrs Simpson, who was a complete nutcase.• Apart, she thought drily, from complete nutcases like myself.• Tania is a major nutcase.• As a result the Eurovision Song Contest delays a hard core of trivia-obsessed nutcases for four hours each year. 