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?]