Graphical computer applications whose individual windows are handled separately by the operating system's window manager. That usually means that each window is displayed as an individual entry in the operating system's task bar or task manager, and that the window does not have a "background" or "parent" window that contains its menu or toolbar, but that each application has its own menu/toolbar. Some task managers summarize windows of the same application in the taskbar. Currently no task-manager handles these windows on a separate taskbar, necessating the use of "tabs" or application-specific taskbar to accomplish this.
See Multiple Document Interface.