lunatic

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++lu·na·tic /ˈluːnətɪk/ noun [countable]  1  CRAZYsomeone who behaves in a crazy or very stupid way – often used humorously 疯狂的人，愚笨的人〔常为幽默用法〕 This hotel is run by a lunatic! 经营这家宾馆的人真是个疯子！2  old-fashionedMENTALLY ILL a very offensive word for someone who is mentally ill 精神错乱的人，疯子〔极具冒犯性的用语〕 a dangerous lunatic 危险的精神病人3. the lunatic fringe British EnglishPPG the small group of people in a political group or organization who have the most extreme opinions or ideas 〔政治团体或组织中的〕极端分子 —lunatic adjective [only before noun] lunatic behaviour 疯狂的行为

Examples from the Corpus

lunatic• The boy and girl probably thought he was a lunatic.• Some lunatic came into the store and shot him.Origin lunatic (1200-1300) Old French lunatique, from Late Latin lunaticus, from Latin luna ( → LUNAR); because people thought mental illness was caused by the moon

lu·na·tic nounChineseSyllable  

very stupid in or – crazy a who way behaves someone Corpus

lunatic
lu‧na‧tic /ˈluːnətɪk/ noun [countable]1. someone who behaves in a crazy or very stupid way – often used humorously:
    This hotel is run by a lunatic!
2. old-fashioned a very offensive word for someone who is mentally ill:
    a dangerous lunatic
3. the lunatic fringe British English the small group of people in a political group or organization who have the most extreme opinions or ideas
—lunatic adjective [only before noun]:
    lunatic behaviour