Definitions for APPæp
Random House Webster's College Dictionary
Computers(informal). an application program; application software.
Origin of app:
An application (program), especially a small one designed for a mobile device.
Origin: From application.
The New Hacker's Dictionary
Short for ‘application program’, as opposed to a systems program. Apps are what systems vendors are forever chasing developers to create for their environments so they can sell more boxes. Hackers tend not to think of the things they themselves run as apps; thus, in hacker parlance the term excludes compilers, program editors, games, and messaging systems, though a user would consider all those to be apps. (Broadly, an app is often a self-contained environment for performing some well-defined task such as ‘word processing’; hackers tend to prefer more general-purpose tools.) See killer app; oppose tool, operating system.