A general term for a program that surreptitiously monitors your actions. While they are sometimes sinister, like a remote control program used by a hacker, software companies have been known to use spyware to gather data about customers. The practice is generally frowned upon.
blackice.iss.net/glossary.php

A technology that assists in gathering information about a person or organization without their knowledge. On the Internet, "spyware is programming that is put in someone's computer to secretly gather information about the user and relay it to advertisers or other interested parties." As such, spyware is cause for public concern about privacy on the Internet.
reach.ucf.edu/~coursdev/cdrom/html/help/glossary.html

This is also known as "adware". It is a hidden software program that transmits user information via the Internet to advertisers in exchange for free downloaded software. The Specialty Alliance Corporation™ does NOT use Spyware in any form or fashion, or will do business with companies that do.
www.calnique.com/glossary.htm

There are concerns that some Web sites and commercial organisations track users' online activity through the use of what is called ‘spyware'. Usually coming in the form of ‘cookies' - these enable the cookie writer to build-up information about what you do and where you go on the Web. Software is available that checks for and removes spyware.
www.btsafersurfing.com/glossary/p_t.html

Software that tracks usage and reports it to others, such as advertisers Usually the tracking is concealed from the user of the software.
www.cba.nau.edu/facstaff/durham-j/glossary_orphanware.htm