Meaning

• A devil or demon; a malignant or diabolical being; an evil spirit.

• A very evil person.

• An enemy; a foe.

  "Religion teaches us to love everybody, be one fiend or friend."

• The enemy of mankind, specifically, the Devil; Satan.

• An addict or fanatic.

  "He's been a jazz fiend since his teenage years."

Meaning

• To yearn; to be desperate (for something).