key_defined.3x man page
key_defined — check if a keycode is defined
int key_defined(const char *definition);
This is an extension to the curses library. It permits an application to determine if a string is currently bound to any keycode.
If the string is bound to a keycode, its value (greater than zero) is returned. If no keycode is bound, zero is returned. If the string conflicts with longer strings which are bound to keys, -1 is returned.
These routines are specific to ncurses. They were not supported on Version 7, BSD or System V implementations. It is recommended that any code depending on them be conditioned using NCURSES_VERSION.