Definition of demon noun from the Oxford Advanced Learner's Dictionary

demon

noun

ˈdiːmən

ˈdiːmən

1 an evil spiritdemons torturing the sinners in Hell2 (informal) a person who does something very well or with a lot of energyHe skis like a demon.He's a demon: he gets up early, he works out, he goes home early, he studies, he works out again…3 something that causes a person to worry and makes them unhappythe demons of jealousy

Idioms

the demon drink

(British English, humorous) alcoholic drink