An implacable or malicious foe; one who is diabolically wicked or cruel; an infernal being; -- applied specifically to the devil or a demon.
- An evil spirit; a demon.
- The Devil; Satan.
- A diabolically evil or wicked person.
- Informal One who is addicted to something: a dope fiend.
- Informal One who is completely absorbed in or obsessed with a given job or pastime: a crossword-puzzle fiend.
- Informal One who is particularly adept at something: a fiend with computers.