A person who is mentally ill or behaves in a wildly unconventional manner.

A person who is enthusiastic about something to the point of being irrational.

उत्साही व्यक्ति

English Usage: He was a madman for speed, always pushing his car to the limit.

Hindi Usage: वह गति के लिए एक उत्साही व्यक्ति था, हमेशा अपनी कार की सीमाओं को बाधित करता।