- The definition of an app is short for application and is software for use on a smart phone or computer.
An example of an app is the Yelp app for the iPhone.
app definition by Webster's New World
app definition by American Heritage Dictionary
Origin: Short for application.
app - Computer Definition
An Application Layer protocol for publishing Web resources associated with periodically updated Web sites. APP builds on the RSS protocol.The Atom Syndication Format is documented in the IETF RFC 4287 (2005). See also Application Layer, IETF, protocol, RSS, and WWW.
(1) (APPlication) The file extension for executable Mac applications. See APP file.
(2) (APPlication) The term has been shorthand for "application" in the IT community for a long time. However, it became popular with the consumer for mobile applications in smartphones and tablets after Apple debuted the iPhone 3G in 2008. It is just as correct to say "iPhone application" as it is "desktop computer app;" although app is shorter, and computer people love to abbreviate. See application and online app store.
(3) (APPlication) In the engineering world, an app can refer to a circuit design, using the word "application" in the context of purpose. For example, "high-voltage apps" means high-voltage circuit designs. The term predates mobile software apps by decades.