For those who are unfamiliar with the name of killer application, also known as killer app, here's the definition: an application that convinces you to purchase a certain hardware component, a certain operating system or a gaming console that would allow you to run that application.
For those of you who like history, the term of 'killer application' was used for the first time for VisiCalc, an application for Apple II platforms, which was bought by thousands of economists.
See also Wiki reference no.1: ^ Scannell, Ed (February 20, 1989). "OS/2: Waiting for the Killer Applications". InfoWorld (Menlo Park, CA: InfoWorld Publications) 11 (8): pp 41-45. ISSN 0199-6649. Early use of the term "Killer Application".