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"An application that proves the usefulness of the underlying technologies"

Defined by Jawed Karem in the speech "YouTube: From Concept to Hyper-growth" held at University of Illinois at Urbana-Champaign ACM Conference, Oct 21, 2006. (www.youtube.com/watch?v=nssfmTo7SZg)
A typical killer application:
- the first spreadsheet application

Killer apps in the internet domain:
- Wikipedia
- LiveJournal
- MySpace
- Flickr
- YouTube
by Papy Jojo March 19, 2007
stands for killer application. Used to describe a game/application that really makes a system/computer.
Halo was the killer app for the Xbox
by where am i? March 13, 2005