Source : Free On-Line Dictionary of Computing

Win32s
     
         A free extension for {Microsoft Windows},
        released by {Microsoft}.  Win32s is a software layer on top of
        Windows which allows {32-bit applications} (e.g. {Mosaic}) to
        run on Windows.  Both stand-alone Windows and {Windows for
        Workgroups} run as 16 bit, and both can use Win32s to run
        32-bit applications.
     
        (1996-07-08)