vl-acad-defun
V Functions
vl-arx-import
Undefines an AutoLISP function symbol so it is no longer available to ObjectARX applications
(vl-acad-undefun 'symbol)
You can use vl-acad-undefun to undefine a c: function or a function that was exposed via vl-acad-defun.
T if successful; nil if unsuccessful (for example, the function was not defined in AutoLISP).