Source : Free On-Line Dictionary of Computing

universal thunk
     
         A software mechanism allowing
        a {Windows 3.1} {application} to call a {32-bit} {dynamically
        linked library} (DLL) under {Win32s}.
     
        The {Windows 3.1} {application} which wants to call an entry
        in a 32-bit DLL instead calls a corresponding entry in a
        {16-bit} DLL.  The programmer must also include {code} to
        detect whether the {32-bit} DLL is loaded.  A {32-bit} {EXE}
        loads the {32-bit} DLL.
     
        See also {Generic Thunk}, {Flat Thunk}.
     
        ["Calling a Win32 DLL from a Windows 3.1 Application", Win32
        SDK Knowledge Base, Article ID Q97785].
     
        [Better explanation?]
     
        (1997-10-11)