daemon
noun
dae·mon
variant spelling of demon
1a
: an evil spirit
angels and demons
b
: a source or agent of evil, harm, distress, or ruin
the demons of drug and alcohol addiction confronting the demons of his childhood
3
usually daemon, mythology
: a supernatural being whose nature is intermediate between that of a god and that of a human being
4
: one that has exceptional enthusiasm, drive, or effectiveness
a demon for work Doug, putting like a demon, had birdies on the third and sixth …— Fred Tupper
5
daemon
: a software program or process that runs in the background
A mailer daemon installed on an e-mail system can respond to a piece of incorrectly addressed e-mail by generating an automated message to the sender that the message was undeliverable.— J. D. Biersdorfer