defundefun is a Lisp macro in `
byte-run.el'. (defun NAME ARGLIST &optional DOCSTRING DECL &rest BODY) Define NAME as a function. The definition is (lambda ARGLIST [DOCSTRING] BODY...). See also the function `interactive'. DECL is a declaration, optional, of the form (declare DECLS...) where DECLS is a list of elements of the form (PROP . VALUES). These are interpreted according to `defun-declarations-alist'. The return value is undefined.