An uninstaller is a program or tool that is part of an application bundle used with Windows operating systems (OS). It allows a user to safely uninstall an application by running a program and following a series of prompts that warn users about the application's removal.
After running an uninstaller, traces of an application still requiring removal may remain, usually in the system registry. These should be removed individually or by using the control panel's add/remove command. In most cases, the uninstall tool is the easiest way to remove an application.
Techopedia explains Uninstaller
Unlike Windows, Mac OS X does not have a system registry, meaning that its application bundles do not require uninstallers. To remove apps, users can simply move folders or icons to the trash.
Additionally, various uninstallers may be downloaded as separate applications. They work with a wide range of other applications, and some even remove registry entries that cannot be removed by original uninstallers.
This definition was written in the context of applications