app

from Jargon File (4.4.4, 14 Aug 2003)

app
 /ap/, n.

   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}.

from The Free On-line Dictionary of Computing (8 July 2008)

application program
app
application software
applications software

   <programming, operating system> (Or "application", "app") A
   complete, self-contained program that performs a specific
   function directly for the user.  This is in contrast to
   {system software} such as the {operating system} {kernel},
   {server} processes, {libraries} which exists to support
   application programs and {utility programs}.

   Editors for various kinds of documents, {spreadsheets}, and
   text formatters are common examples of applications.  Network
   applications include clients such as those for {FTP},
   {electronic mail}, {telnet} and {WWW}.

   The term is used fairly loosely, for instance, some might say
   that a client and server together form a distributed
   application, others might argue that editors and compilers
   were not applications but {utility programs} for building
   applications.

   One distinction between an application program and the
   operating system is that applications always run in {user
   mode} (or "non-privileged mode"), while operating systems and
   related utilities may run in {supervisor mode} (or "privileged
   mode").

   The term may also be used to distinguish programs which
   communicate via a {graphical user interface} from those which
   are executed from the {command line}.

   (2007-02-02)