A "killer app" is jargon in the computer industry for an application program that intentionally or unintentionally gets you to make the decision to buy the system the application runs on. A classic example of a killer app was the spreadsheet program, the first of which was called VisiCalc, followed later by Lotus 1-2-3. The spreadsheet application helped introduce the personal computer into the department level of large and small businesses. A killer app can refer to a generic type of application that hasn't existed before, to a particular product that first introduces a new application type, or to any application with wide appeal.
When a new kind of computer hardware product comes out, such as a hand-held computer, manufacturers offer or hope to entice others to develop what they believe will be the killer app that will motivate potential customers to buy the new computer. In recent ads, IBM says that the killer app for e-business (which is both a concept and an array of Internet products and services that IBM sells) is "an application deployed over the Web that makes it easier to do the things you already do." Clearly, the Web browser and the Internet servers it communicates with became the killer app of the 1990s.