Definition - What does Orphan File mean?
An orphan file is a file that has been left over after its parent application has been removed or uninstalled from the system. Orphan files may include files with a .dll extension.
The most common reason for the presence of an orphan file is incomplete uninstallation of its parent application, usually the result of manually deleting the application. Hard drive cleanup utilities will often manage orphan files as they scan for temporary files.
Techopedia explains Orphan File
Users can delete an orphan file safely only if no other applications require it. Sometimes .dll files are used by more than one application or even by the operating system. If deleted, programs requiring the .dll file may cause errors or fail to function at all until the file is restored to the system. For this reason, and because orphan files are often small in size, leaving them in place may be a safer course of action.