type: system constant location: built-in source file: xlinit.c and xlsym.c Common LISP compatible: no supported on: all machines
*UNBOUND* is a system constant that is used to indicate when a symbol has no value. *UNBOUND* is set to the value *UNBOUND*. This means that the system thinks the symbol *UNBOUND* has no value.
*unbound* ; error: unbound variable (setq a 5) ; returns 5 a ; returns 5 (setq a '*unbound*) ; returns *UNBOUND* a ; error: unbound variable