Definitions for "Killer Application"
an application (including hardware) that fundamentally alters business by generating its own independent global market. The most outstanding example in the Internet is E-mail.
an application that revolutionises the way the computer(internet) is used
a program that takes advantage of a computing platform to create an innovative product that is unavailable anywhere else
a new product or service that establishes a strong and new market category, dominates it, and brings significant returns to investors
Keywords:  buy, software, people, order, program
Software so useful that people will buy it in order to obtain the program or service it provides.