unintern

(unintern symbol &optional package)

Removes symbol from the member table of package (the current package by default): find-symbol stops answering it as the package's own, and when the package was the symbol's home, symbol-package answers nil from then on. An imported symbol loses only its redirect; either way it stops being external and shadowing. Returns t when the symbol was present, nil when it was not -- an inherited symbol, or one homed elsewhere and never imported. Uninterning a shadowing symbol that hid two different inherited symbols of the same name would leave a name conflict, so that signals a package-error and changes nothing. So does a designator that names no package, on every backend.

Deviation from Common Lisp: a symbol is its spelling here, so interning the same name into the package again homes the old symbol again (Common Lisp mints a distinct symbol). On the compiled backends the removal is recorded for the packages the program creates with make-package (a read/compile-time package is frozen there, and unintern answers nil), and symbol-package keeps reading the qualifier off the spelling.