Simplified Common Lisp reference
Symbol class: Functions, Evaluation, Flow Control, Definitions and Syntax
Symbol type: special form
labelsbindingsbody(zero or more) => an object
Argument description:
bindings list containing function definitions
body program code in which definitions above are effective, implicit progn

LABELS is special form for local function binding. Bindings can be recursive and can refer to each other. Each binding contains function name, arguments, and function body. See FLET, DEFUN, LAMBDA.

(labels ((fact2x (x) (fact (* 2 x)))
         (fact (x) (if (< x 2) 1 (* x (fact (1- x))))))
  (fact2x 3))
 => 720
Function indexFull documentation for labels (HyperSpec)