Definition of Demon

Noun: demon dee-mun

An evil supernatural being
- devil, fiend, daemon, daimon
A cruel wicked and inhuman person
- monster, fiend, devil, ogre
Someone extremely diligent or skilful
"he worked like a demon to finish the job on time"; "she's a demon at maths"
(computing) a program that runs automatically or on a schedule without user interaction
- daemon