Redefine language from scratch (y/n)?

pozorvlak@delirium:~> clisp
  i i i i i i i       ooooo    o        ooooooo   ooooo   ooooo
  I I I I I I I      8     8   8           8     8     o  8    8
  I  \ `+' /  I      8         8           8     8        8    8
   \  `-+-'  /       8         8           8      ooooo   8oooo
    `-__|__-'        8         8           8           8  8
        |            8     o   8           8     o     8  8
  ------+------       ooooo    8oooooo  ooo8ooo   ooooo   8

Copyright (c) Bruno Haible, Michael Stoll 1992, 1993
Copyright (c) Bruno Haible, Marcus Daniels 1994-1997
Copyright (c) Bruno Haible, Pierpaolo Bernardi, Sam Steingold 1998
Copyright (c) Bruno Haible, Sam Steingold 1999-2000
Copyright (c) Sam Steingold, Bruno Haible 2001-2006

[1]> (defun car (x) (cdr x))

** - Continuable Error
DEFUN/DEFMACRO(CAR): # is locked
If you continue (by typing 'continue'): Ignore the lock and proceed
The following restarts are also available:
ABORT          :R1      ABORT
Break 1 [2]> continue
WARNING: DEFUN/DEFMACRO: redefining function CAR in top-level, was defined in
         C
CAR
[3]> (car '(3 4))
(4)
[4]> (defun defun (x) (+ 3 x))
DEFUN
[5]> (defun 7)
10

Bad. Ass.

[Those of you who don't speak Lisp may find a measure of enlightenment here. Should be reasonably accessible.]