- (archaic or poetic) enemy
- devil, demon, fiend
- a term for another person (or thing) implying strong dislike or annoyment
The plural fjendur is used with the sense of “enemies”, but fjandar for “devils”. In the sense “enemy”, the word is rarely encountered in the singular anymore. In the sense “devil”, it is often used in the singular with the definite article to indicate the Devil (Satan).