ˈdiː.mən ˈdʌɪməʊn ˈdaɪˌmoʊn ˈdiː.mən ˈdɛvəl fiːnd ˈmɒnstə(ɹ) ˈmɑnstɚ ˈəʊ.ɡə ˈoʊ.ɡɚ an evil supernatural being someone extremely diligent or skillful he worked like a demon to finish the job on time she's a demon at math a cruel wicked and inhuman person