stands for "Remove Windows Activation Technologies." It is a tool created to permanently deactivate the Windows Activation Technologies (WAT) service, which is responsible for verifying the legitimacy of a Windows license.
Many versions of Removewat found online are camouflaged malware designed to steal data or compromise the host machine.
Removewat 2.2.9 was a popular, albeit illegal, solution for many users looking to bypass Windows activation in the past. While it was effective at turning off notifications, the risks of malware, system instability, and legal issues far outweigh the benefits.