W: Windows
I: Icons M: Menus P: Pointing device
This is a term oftimes used to refer to the User Interface GUI interfaces commonly found on contemporary desktop systems.
If you're going to get into doing this sort of thing with Tcl, use Tk (or fltk, or ...) See also Playing WIMP for a toy icon system.
See also: [L1 ] for "weakly interacting massive particles".