Noun fiend has 3 senses
- monster, fiend, devil, demon, ogre - a cruel wicked and inhuman person
--1 is a kind of unpleasant person, disagreeable person
--1 has particulars: demoniac
- devil, fiend, demon, daemon, daimon - one of the evil spirits of traditional Jewish and Christian belief
--2 is a kind of evil spirit
--2 has particulars: incubus; succubus, succuba; dybbuk, dibbuk
- fanatic, fiend - a person motivated by irrational enthusiasm (as for a cause); "A fanatic is one who can't change his mind and won't change the subject"--Winston Churchill
--3 is a kind of enthusiast, partisan, partizan
,