Meta-.

[GLS at MIT-AI (Guy L. Steele, Jr.)]

In the version of ZWEI on system 29.95 NWS, with microcode 669, on LISP Machine Eight:

I find it very frustrating that when I have several files loaded
which define a function of the same name that I cannot conveniently use
Meta-. to get around within a single file.  I suggest that Meta-.,
on finding more than one definition, should always prefer a definition
in the current buffer to one in another buffer.