A program that runs continuously in the background, until it is activated by a particular event. A common example are programs that handle email. The word daemon is Greek for "an attendant power or spirit."
Articles on KurzweilAI.net that refer to DaemonThe Technological Singularity By Vernor Vinge
Global Cyberspace and Personal Memespace By Bruce Damer
From The Enlightenment to N-Lightenment By Michael Buerger