Variable: meta-prefix-char
meta-prefix-char is a customizable variable defined in keyboard.c.
Value
27
Documentation
Meta-prefix character code.
Meta-foo as command input turns into this character followed by foo.
Probably introduced at or before Emacs version 1.12.
Source Code
// Defined in /usr/src/emacs/src/keyboard.c
DEFVAR_LISP ("meta-prefix-char", meta_prefix_char,
doc: /* Meta-prefix character code.
Meta-foo as command input turns into this character followed by foo. */);