Variable: outline-level
outline-level is a variable defined in outline.el.gz.
Documentation
Function of no args to compute a header's nesting level in an outline.
It can assume point is at the beginning of a header line and that the match
data reflects the outline-regexp.
Probably introduced at or before Emacs version 19.19.
Source Code
;; Defined in /usr/src/emacs/lisp/outline.el.gz
(defvar outline-level #'outline-level
"Function of no args to compute a header's nesting level in an outline.
It can assume point is at the beginning of a header line and that the match
data reflects the `outline-regexp'.")