WordWeb Online

1. A person who is regarded as eccentric or mad
   - nutter [Brit, informal], wacko [informal], whacko [informal], mentalist [Brit, informal], nutcake [US, informal], nutjob [informal], wackjob [N. Amer, informal], basket case [informal], nutbar [N. Amer, informal], wackadoodle [N. Amer, informal], fruitcake [informal]

See also: crazy [N. Amer, informal], headcase [informal], looney [informal], loony [informal], lunatic, madman, maniac, nutcase [informal]

Type of: dag [Austral, NZ, informal], eccentric, eccentric person, flake [N. Amer, informal], geek [informal], oddball [informal]