crazy person

noun
  1. An individual who is perceived to behave in an irrational, unpredictable, or mentally unstable manner. noun
    The neighbors thought he was a crazy person because he talked to himself loudly in the garden.
    She was labeled a crazy person for her eccentric fashion choices and unconventional lifestyle.
  2. A colloquial term used to describe someone who is extremely enthusiastic or passionate about something, often to the point of obsession. noun
    He's a crazy person when it comes to collecting vintage cars; his entire garage is filled with them.
    She's a crazy person about fitness, spending hours at the gym every day.