head case

noun informal

madman/madwoman, maniac, lunatic;

informal loony, nut, nutcase, nutjob, fruitcake, cuckoo, basket case, headbanger, schizo, crank, crackpot, oddball, weirdo, weirdie, sicko;

British, informal odd bod, nutter;

Scottish, informal radge;

North American, informal screwball, crazy, kook, geek, nutso, meshuggener, wacko, wack;

US, informal wing nut, wackadoo, wackadoodle;

North American, & Australian, New Zealand, informal dingbat;

informal , dated case.

headcase Oxford Dictionary of English