A Windows product update (for example, a critical update, a security patch, or a hotfix) is an executable (.exe) file that contains one or more system files that you can apply to Windows to correct a specific problem. 

 Source: Microsoft Microsoft Hotfix

Microsoft’s term for “patch.”

 Source: NIST NIST SP 800-44 Version 2

A hotfix is a temporary fix to a software bug that is released without the usual extensive testing that accompanies a full software update. It is generally used to address a critical issue that needs to be resolved quickly.