Below are some SharePoint Dictionary App Words of the Day:
App
Features that a site owner or administrator can add to a SharePoint Site, such as document libraries, lists, calendars and tasks.
App catalog
A SharePoint document library that administrators can use to distribute apps for Office and SharePoint to users.
App custom action
A category of a custom action that is added to a host site by an app for SharePoint and which links to additional functionality that is contained by the app.
App for SharePoint
A cloud-enabled app that adds rich, scenario-focused functionality into a SharePoint environment.
App part
A module of an app for SharePoint that can be embedded on a site page to show the functionality of the app.
App web
A sub-web site where the SharePoint elements of an app are deployed when the app is installed on a host web.