WordPress at a glance
filter is not described

blog_redirect_404 filter-hook . WP 3.0.0

Filters the redirect URL for 404s on the main site.

The filter is only evaluated if the NOBLOGREDIRECT constant is defined.

Usage

add_filter( 'blog_redirect_404', 'filter_function_name_352' );
function filter_function_name_352( $no_blog_redirect ){
	// filter...

	return $no_blog_redirect;
}
$no_blog_redirect(string)
The redirect URL defined in NOBLOGREDIRECT.

Where the hook is called

maybe_redirect_404()
blog_redirect_404
wp-includes/ms-functions.php 2067
if ( is_main_site() && is_404() && defined( 'NOBLOGREDIRECT' ) && ( $destination = apply_filters( 'blog_redirect_404', NOBLOGREDIRECT ) ) ) {

Where the hook is used (in WP core)

Does not used.